CA2092403A1 - Oligo(2-alkenyl azlactones) - Google Patents

Abstract

This invention provides novel azlactone-functional oligomers of 2-alkenyl azlactones in which oligomerization has occurred predominantly via the 2-alkenyl group. Oligomerization of the 2-alkenyl group provides oligomers having 2 to 15 mer units with predominantly carbon-carbon backbone segments. Oligomerized in this fashion, the novel compositions possess azlactone groups which can be reacted with nucleophiles in the normal ring-opening sense. The oligomers are prepared by a novel process in which both Lewis and Bronsted acidic catalysts are effective. The reactive oligomers find utility as crosslinking agents for polymers containing azlactone-reactable nucleophilic groups.

Description

~ WO92/~7012 PCTrUS9l/~4 . !, . . .
.2.~.0~
OLIGOt2-AL~ENYL AZL~CTONE5) -:
Field of the Inventlon This invention relates to a reactive oligomer obtained by the acid catalyzed oligomerization of 2-alkenyl azlactones. The novel reactive oligomers find utility as crosslinking agents in pressure sensitive adhesives.

Back~round of the Invention Addition polymerization reactions of vinyl monomers can involve anionic, ~ree radical, or cationic intermediates. The reaction mechanism for polymerization is illustrated in the scheme below in which I represents an initiator; the asterisk signifies a negative charge, a free ~¦ 15 radical, or a positive charge; and Z represents hydrogen, halogen, or an organic group.
- Initiation:
z I* + CH2=CHZ > ICH2CH*

Propagation:

.. , z Z Z
ICH2CH* + n CH2~CHZ - > I~CH2CH)nCHzCH*

Termination:

Z Z
I(CH2CH)~CH2CH* > Inactive or Dead Polymer + I'*

Distinct initiation, propagation, and termination phases of a polymerization constitute a so-called chain reaction when the termination reaction provides an ~ctive by-produc*
- (designated I'* above) capable of initiating another -~ polymerization sequence in addition to inactive polymer.
. .

,, ~,, .

.
;, : ' ~' :': '':

' WO~_07012 PCTrUS91/~
~ 2~4~3 . .
Whether polymerization involves anionic, free radical, or cationic intermediates is largely determined by the nature of 2 in the vinyl monomer. Although many vinyl monomers are efficiently polymerized by free radical initiation, most polymerize ionically, if at all, by only one kind of active center. Methyl acrylate (in which 2-CO2CH3), for example, polymerizes efficiently by radical and anionic initiation, but essentially not nt all by cationic means. Generally speak~ng, Z groups which provide elsctronic and resonance stabilization by releasing electron density facilitate polymerization via cationic intermediates, while Z groups which withdraw electrons stabilize anionic intermediates.
That the aziactone group is electron withdrawing relative to hydrogen and 2-alkenyl azlactones (2-oxazolin-5-ones) possess 2-alkenyl groups which are electron deficient relative to ethylene are indicated by at least two factors. First of all, 2-vinyl-4,4-dimethylazlactone (VDM) can be effectively polymerized employing free radical techniques (cf. J.R. Rasmussen, S.M.
Heilmann, and L.R. Krepski, "Polyazlactones" in Encvclo~edia of Polymer Science and Enqineç~Ln~, Volume 11, Second Edition, John Wiley & Sons, Inc.: New York, 1988, pp.
558-571). An indication of the electron supplying/withdrawing behavior OS the azlactone group and the propensity of VDM to polymerize by ionic active centers can be obtained by examining free radical copolymerization with styrene. When this experiment was conducted in the above reference, the "e" value or measure of the polarity of the vinyl group in VDM was determined to be +0.65. By comparison with the e value for methyl acrylate of +0.64 (cf. R.Z. Greenley, "Q and e Values for Free Radical Copolymerization of Vinyl Monomers and Telogens" in Polymer - ~andbook edited by J. 9randrup and E.H. Immergut, Third 35 Edition, John Wiley & Sons, Inc.: New York, 1989, II-267 to .! II-274~, the azlactone heterocycle possesses approximately .

. r ' 't ' ' ' "

' ~ ~O9~ ~12 PcT/uS9t/o~4 _, 3 ~ ~ g ;~
the same electron withdrawing capability as the carbomethoxy group and would be expected to stabilize anionic intermediates.
Another indication of the relative electron deficiency of the 2-al~enyl group in VDM can be obtained from its 13C-NMR spectrum. X. Hatada et al., Makromol.
Chem., 178, 2413-2419 (1977) have utilized the relative position of the resonance of the 1-carbon of a terminal olefin to successfully predict whether the ole~in will polymerize by anionic or cationic initiation. Using the carbon disulfide 13C resonance as a reference signal (193.7 ppm relati~e to the more traditional tetramethylsilane reference), these workers observed that monomers with 1-carbon resonances of about 100 ppm upfield, i.e., to the ~5 right or at higher energy, from the carbon disulfide resonance polymerized by cationic intermediates. ~onomers with 1-carbons resonating at about 70 ppm responded to anionic initiation. Since VDM exhibits a l-carbon resonance at 64.7 ppm on this scale, one would predict that 2-alkenyl azlactones would respond to anionic but not to cationic polymerization techniques.
Reports exist of electron deficient olefins which oligomerize or polymerize in the presenca of acid. Tomalia et al. (Polvmer J., 1980, L~, 661) motivated by the observation "that a variety of unldenti~ied polymers, gels, or oligomeric syrups were readily formed by merely allowing 2-alkenyl-2-oxazolines to come in contact with Bronsted acids at room temperature" initially reported the oligomerization and polymerization of 2-isopropenyl-2-oxazoline (IP0). IP0 is an electron deficient olefin as indicated by the e value of +0.34 for the 4,4-dimethyl derivative (Polvmer Handbook, II-271) and a 3C-MMR l-carbon resonance of 73 ppm upfield from the carbon disulfide resonance. They reported the formation of cyclic - 35 dimers in the presence of strong monoprotic Bronsted acids such as trifluoromethanesulfonic-acid and low molecular .. .... . . .. ~

.

~ :
.

~ . .
:
i W0~_~7012 PCT/US91/0~4 -. ~-' 4 2~9~3 weight (MN = 900 to 2500) polymers when strong diprotic - ~ Bronsted acids such as sulfuric acid were utilized. These results are summarized in the Scheme below:

; ~ N + ~ ~ N Q

',' 10 ~ ~I
-: H
~ + 3 ~ ~

X ~ C~3 G I + I CEI
X--CF3S0 ~
( ~ H
Z CU3 ~ N ~

I CH3 o--~ I + I ~ ¦
x + ~ ~ x~ ~CH3 O ~ ~ CH3 ~ gof L~ CH3 6 tO 20 ~ .

.:
~ .
~,:`, ,, :
;.. .
' ' ,.~;.

~ , .

}WO 07012 PCT/US91/~4 }
- 5 20~2~

With the exception of the six-membered ring dimer, all proposed structures involve the oxazoline nitrogen as a main-chain atom resulting from Michael or 1,4-addition of the nitrogen to the enone-like system of the r71 5 Z-isopropenyl-2-oxazolinium species followed by proton transfer from nitrogen to carbon.
Similarly, Saegusa et al. (Polymer J., 1987, 19, 557) reported, based on the lH-NMR spectrum, that 2-vinyloxazolinium fluorosulfonate, prepared $rom 10 2-vinyl-2-oxazoline and fluorosulfonic acid, prov$ded a mixed polymer of predominantly monomer units in which nitrogen was present in the main-chain (80S) and a minor amount of vinyl polymerized units (20%).

~ CH2C~2~

~chael ~r~yl U~ unLs 8~MMARY OF T~E INVENTION
~ riefly, this invention provides an azlactone-functional oligomer having 2 to lS units of which at least 30 mole percent are 2-alkenyl group polymerized units. ~he nove~ azlactone-~unctionnl oligomers of 2-alkenyl azlactones ~re the product of oligomerization which has occurred predominantly via the 2-alkenyl group. Oligomerization of the 2-alkenyl group provides oligomers with predominantly carbon-carbon backbone segments. Oligomerized in this fashion, the novel compositions possess azlactone groups which can be reacted with nucleophiles in the normal ring-opening sense.
~ In another aspect of the invention, the oligomers -~ 35 are prep~red by a novel process in which both Lewis and -- Bronsted acidic catalysts are effective. The reactive . . .

.

WO~7012 P~TrUS9l/0~4 2~92~3 .
oligomers find utility as crosslinXing agents ~or polymers containing azlactone-reactable nucleophilic groups.
In contrast to the acid catalyzed oligomerization ~;j and polymerization of 2-alkenyl-2-oxazolines in which predominantly Michael units were formed, the 2-alkenyl azlactones (2-oxazolin-5-ones) of the invention yield oliqomers containing predominantly vinyl units, i.e., carbon-carbon backbones.
ln this application:
"alkyl" means the monovalent residue remaining after removal of a hydrogen atom from a saturated linear or branched chain hydrocarbon having 1 to 14 carbon atoms;
"aryl" means the monovalent residue remaining after removal of a hydrogen atom from an aromatic compound (single ring and multi- and fused-cyclic) having 5 to 12 ring atoms and includes substituted aromatics such as lower alkaryl and aralkyl, lower alXoxy, N,N-di(lower alkyl)amino, nitro, cyano, halo, and lower alXyl carboxylic ester, wherein "lower" means C-l to C-4;
"azlactone" means 2-oxazolin-5-one ~roups of Formula I and 2-oxazin-6-one groups of Formula II;

~, --1 /Y ~ /
25 . ~O ~ C ~ - C ~C\
O C~
: O
- I

"cycloalkyl" means the monovalent residue remaining aftèr removal of a hydrogen atom from a saturated cyclic hydrocarbon having 3 to 12 carbon atoms;
- "lower alkyl'i means C-l to C-4 alXyl groups;
"Michael addition" or "Michael react~on" means the - catalyzed or uncatalyzed addition of a "Michael donor", .

'J
~ .
.' ~ ' , , , . . . .

~ ) - WO~ )7012 PCTrUS91/~

7 ~ 2 ~ 0.4~
illustrated by trifluoroacetate ion (III) in the equation below, to a "Michael acceptor", illustrated by protonated 2-vinyl-4,4-dimethylazlactone (VDM) (IV) in the equation - below, to form a "Michael adduct" reaction product (V):
~ 5 , CF3Co~ = ~G
m IV

"Michael acceptor" means the electrophilic reactant in a Michael reaction;
"Michael adduct" means the product of a Michael reaction;
"Michael donor" means the nucleophilic reactant in -~ a Michael reaction;
.~` "oligo (2-alkenyl azlactones)" means polyaddition ~ products of 2-alkenyl azlactones in which the products are i characterized as having had addition occur at least once, i.~., a dimer possesslng a number-average molecular weight of at least 278 in the case o~ VDM, to about ~ourteen times, i.e., a flfteen-mer possessing a number-average molecular l weight of about 2000;
j. .3 "oligo (VDM)" means ~ny oligomer of VDM having 2 to 15 mer units; and "predominantly" means at least 30 mole percent, prQferably at least 50 mole percent, and more preferably at least 80 mole percent.
As disclosed herein for the first time, VDM and j - 35 other 2-alkenyl azlactone monomers have been observed to undergo oligomerization when exposed to certain acid ...

~ .
, ' W092/070~2 PCT/US91/~4 catalysts. Since effecting oligomerization/polymerization of a monomer by acidic catalysts is normally regarded as involving cationic intermediates, this result was unexpected.
;:~
DESCRIPTION OF TFE DRAWINGS
FIG. 1 is a high pressure liquid chromatogram measuring ultraviolet light absorption versus time for the partially hydrolyzed oligo(VDM) sample of Example 1.
FIG. 2 reprQsents a comparison of the IR spectra of films of oligo(VDM) of Example 3 (ZA), poly(VDM) of ; Example 19 (2B), and 2-ethyl-4,4-dimethylazlactone (EDM) (2C). Spectra were obtained using a Perkin Elmer 983 Ratio Recording Infrared Spectrophotometer.
FIG. 3 represents a comparison of the lH-NMR
`spectra of deuterochloroform solutions of oligo(VDM) of Example 3 (3A) and poly(VDM) (3B). Spectra were obtained using a Varian XL-400 Spectrometer.
FIG. 4 represents a comparison of the l3C-NMR
~pectra of deuterochloroform solutions of oligo(VDM) of Example 3 (4A) and poly(VDM) (4B). Spectra were obtained using a Varian XL-400 spectro~eter. The signal-to-noise ratio for oligo(VDM) was improved by recording transients over an eight hour perlod.
FIG. 5 represents a comparison of the ultraviolet ~W) spectra of acetonitrile solutions of oligo(VDM) of Example 22 (SA), poly(VDM) (5B), and EDM (5C). W spectra were obtained using a Perkin-Elmer Model 330 Spectrophotometer. The absorptivity for oligo(VDM) at 331 nm was 2.52 l/g-cm.
FIG. 6 represents a comparison of the size exclusion gel permeation chromatograms of oligo(VDM) prepared by conditions outlined in Examples 21 (6A), 22 ~6B), 23 (6C), and 24 t6D). GPC's were obtained in tetrahydrofuran solution using a Hewlett-Packard 1090-LUSI
-~ instrument. The column set utilized was specifically .. . .

-~ WO9~07012 PCTrUS91/0#~
q '~92~

designed for the separation of materials of molecular weight of less than lo,OOO. Columns utilized were three 500 A
columns (1 x 50 cm + 2 x 25 cm) from Jordi Associates (Millis, MA). Molecular weight data were based on calibration using polystyrene standards available from Pressure Chemical Co. (Pittsburgh, PA).

D~AI~ED DESCRIPTION OF T~E INVENTIO~
The present invention provldes novel azlactone-functional oligomers possessing structures sielected ~rom the group consisting of:
A) oligomers possessing structures depicted by general Formula VI
.. i R4 O
R
R ~ ~

Z0 ~ ~ G Vl O N

O

; wherein j Rl and R2 independently represent an alkyl group of 1 to 14 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, an aryl group of 5 to 12 ring atoms, or Rl and R2 taken together with the carbon atom to which they ar~ joined form a carbocyclic ring of 4 to 12 ring ~toms;
R3 and R4 are independently hydrogen or lower alkyl;
. n is O or l;
, ~.

. -, , . . ~ .
,~,s - . , .'~,:''~1 , '. WO~7012 PCT/US91/0~
, . ~
" '"" / 2~`~2g~
. . ~ .
Az is a symbol for an azlactone group bonded in the 2-position in which R1, R2, R3, ~4, and n are as defined above:
~,, ~ .
- 5 Rl !, N_I R
_ // ~R3 :' 10 ~
; O

~¦ G independently can be hydrogen, methyl, and groups "`,r,~ selected from -CH2CHGAz, -CH2CG(Az)CH2CHGAz, ~ 15 -CH2CG(Az)tCH2CG(Az)]pCH2CGAz, and p can have integral .: values from 0 to about 12, with the proviso that the extent of oligomerization does not exceed a total number-average molecular weight of about 2000 for the oligomers depicted by Formula VI;
' 20 r can be o or 1; and q can have integral values from l to about 12.
'~ B) oligomers possessing structures depicted by --l ' general Formulae VIIA and VIIB
f G
XCH2CAZ CH2--C-Az G

VIIA YIIB
wherein X is the covalently bonded counter ion or gegenion of a 3~ Bronsted acid whose pKa is less than 1.2, or X can be a . 3-quaternized 2-alkenyl azlactone group of Formula VIII

, , :, ., ... .

' --- , .. . . .

': ` .

WO. J7012 PCM~S91/0664 ; . .
- ~1 2 ~ 9 ~
., / R5 ~ ~/
~=N Rl j in which Rs can be hydrogen or methyl and all other symbols are as previously defined; and Az and G are as defined above, QXcept that at most one G can be hydrogen or methyl in Formula VIIA when X i9 not a 3-quaternized 2-alkenyl azlactone group, and in Formula YIIB
G cannot be H or CH3.
~, C) oligomers possessing structures depicted by general Formula IX
: Az I .
C~C--CH2 ( ~/\`J lX

G Az Jq wherein Az, G and q are as previously de~ined.
I The oligomers of the invention are prepared by the ¦ cid catalyzed oligomerization Or 2-al~enyl azlactones of ~: Formula X.
~ R5 =~ .

3 5 ~R2 . ' . . .

,.~ - .
,, .

:
. ., .

WO ~7012 PCTrUS91/0~
2~92~
,z wherei~
Rl, R2, R3, R4, R5, and n are as defined above.

Useful 2-al~enyl azlactones include:
2-vinyl-4,4-dimethyl-2-oxazolin-5-one talso called 2-vinyl-4,4-dimethylazlactone or VDMl, 2-isopropenyl-4,4-dimethyl-2-oxazolin-5-one, 2-vinyl-4-ethyl-4-methyl-2-oxazolin-5-one, 10 2-vinyl-4,4-dimethyl-1,3-oxazin-6-one, and others whose preparations are disclosed in U.S. Patent No. 4,305,705. A
preferred 2-alkenyl azlactone is VDM (available from SNPE, Inc., Princeton, NJ).
Both Bronsted and Lewis acidic materials are ,. .
effective catalysts for the oligomerization. Bronsted acids are classical proton donating materials, and useful c~talysts are relatively highly acidic possessing pKa's of less than about 1.2. Useful Bronsted acid catalysts include sulfuric acid, hydrogen chloride, hydrogen bromide, hydrogen iodide, trifluoroacetic acid, trichloroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, perchloric acid, and ethanesulfonic acid. Useful Lewis acids (which broadly encompass Bronsted acids in their role as electron pair acceptors) include aluminum chloride, zinc chloride, boron tri~luor~de, antimony pentachloride, titanium tetrachloride, and iodine. In general the rate of oligomerization is directly related to acid strength of the catalyst. A further consideration for the choice of a proper catalyst, however, is the influence that very strong acids, e.g., pKa's < -3, have on the stability of the azlactone oligomeric product. Employment of these very strong acids requires that the azlactone oligomeric product be handled in a water-free environment, as the product will quicXly hydrolyze with adventitious moisture in the presence of these very strong acids. Although longer oligomerization times are required with more weakly acidlc catalysts, the ; -- . .
. . .. . , , .. .. , .. . .... , _ ... _ _._ _ . ...

WO~ ~7012 PCTrUS91/0~
. ., ~ . .
2~92~3 l3 resultant oligomeric azlactone product is less sensitive to hydrolysis. Preferred catalysts are trifluoroacetic acid - and boron trifluoride for 2-vinyl ~R5 = H) substituted ; azlactones; ethanesulfonic acid is preferred for 2-isopropenyl (RS = CH3) substituted azlactones. Useful amounts of the catalysts are from 0.1 to 50 mole percent (based on 2-alkenyl azlactone), preferably l.0 to 25 mole percent, and more preferably ~rom 1.0 to lo mole percent.
Although the oligomerization reaction can be conducted without solvent, for purposes of control and uniformity of product a solvent is generally employed.
Aside from the desirability of an effective solvent to dissolve both reactants and oligomeric products, the solvent contains no hydroxyl, thiol, or amine groups capable of -' 15 undergoing a ring-opening reaction with the azlactone ; heterocycle. Useful organic solvents include chloroform, dichloromethane, 1,2-dichloroethane, toluene, diethyl ether, acetone, methyl ethyl ketone, ethyl acetate, acetonitrile, especially acetic acid, and mixtures thereof. The nature of t~e solvent is not without affect on the oligo~erization ~I process, and generally higher rates of oligomerization are ,?`.~, observed with increasing solvent dielectric constant. A
- j possible rationale for this observation is that the oligomerizing species are ionically charged, and ions simply are more stable in higher dielectric med$a. Acetic acid was specifically noted as being an effective solvent because of ; its high dielectric constant and because it may actually I participate in the oligomerization reaction by creating enolizable hydrogens through initial Michael addition, vide in~ra. Useful concentrations of these solvents are generally from 0.9 to 0.1, preferably 0.7 to 0.2, and more - preferably 0.5 to 0.3 weight fraction of the reaction solution.
~ he oligomerization reaction rate can also be -:~ 35 enhanced by increasing the temperature. ~referred reaction ~-~ temperatures range from 20 to 100C.

-, . ~ . .

~,~ WO92/07012 PCT/US91/~4 . ~ .~ ' .,~ .. ;
2~92403 Corresponding reaction times vary depending on thepreviously mentioned factors such as catalyst, catalyst concentration, solvent, solvent concentration, and reaction temperature. Generally reaction times range from a few ~ 5 hours to several days. Progress of reaction is conveniently monitored by gas chromatography observing the disappearance of 2-alkenyl azlactone relative to the solvent.
~ he complexity o~ the oligomerization r~action is evident from the hplc chromatogra~ of FIG. 1 in which the 10 presence of more than 30 products can be detected. Some of these are also highly colored as indicated by the lower trace in Figure 1 suggesting significantly different kinds of structures in which electrons can be highly delocalized.
While not wishing to be bound by any explanation or reaction mechanism and yet to disclose the invention in as precise terms as possible, the following characteristics are supported by the experimental examples.
1) That oligomerizing monomer is the protonated ; 2-alkenyl azlactone is supported by the fact that only strong acids capable of protonating (or engaging in acid-base complexation in the case of Lewis acids and to facilitate discussion only protons will be considered in subsequent explanations) the nitrogen of the azlactone function are effective catalysts. Also, increasing the concentration of acid (and protonated azlactone) dramatically increases the rate of oligomerization.
2) The overall oligomerization begins by Mich~el addition to the protonated 2-alXenyl azlactone to generate reactive ketenaminal structures. In an inert solvent the protonated monomer generally has two nucleophilic agents with which it can react, the counter ion or gegenion (X~) of the acid catalyst and the 2-al~enyl azlactone (represented by VDM below):

':.

:, .

, .. ~j . .

WO ' ~7012 PCI~/US91/0464~
- 2~9~3 1s - 5 =~-- Mc 0~

X~/ \~VDM X
10 X/ \~NH =~
Mc R.~ re ~= N Mc~--NH Me ~Me Ke~e~ ~ e ~¦ 1` ,1 1` Me H X N J~MC
~ _ < Stabil~zing //
X ~ N M A~c~ne ~ ~ O

O
O

, .

wherein in all charts Me = methyl ; X and VDM are as previously defined.
An important aspect of the above reactions is that initial Michael addition to form the reactive ketenaminals is favored strongly because the Michael adducts can undergo stabilization because of the tautomeric equilibrium possible ;~ when a proton can shift from azl~ctone nitrogen to alpha-carbon of the original 2-al~enyl group. That this 3S ~tabilization is very important was strongly supported by the ~nability of a methylating agent ~methyl :~ j .. .~ .
.'.' .

-~ ` WO~ ~7012 PCTt~S91~0~
- .
~, .
~ 2~92~03 p-toluenesulfonate) to initiate oligomerization; analogous shifts of methyl groups do not generally take place.
That hydrogens on carbons adjacent to azlactone groups can enolize to reactive ketenaminal forms and -~q 5 participate in the oligomerization was clearly supported by - incorporation into the oligomeric framework of azlactones possessing saturated alkyl groups at position-2 (see Example 27).
Whether the gegenion or VDM adds to the protonated YDM is largely determined by the nature and nucleophilicity of the gegenion. With carboxylate ions, for example, the gegenion reaction can be very important, whereas with stronger acid gegenions such as perchlorate, sul~ate, and triflate the gegenion reaction may be less important.
3) The ketenaminals engage in oligomerization with ~- protonated VDM in the following manner:
Case 1: Gegenion Michael addition : :, ,.. .

.

, . ;.
..;

'd;
~,-,~ , , ' .

; WO '~7012 PCr/VS91/0664~
. ' , ~92 ~7 --~ MeX~ N~MC
~yNH 0 /~Me x \~ n Mc~ Ob~.Me b c 0 -H~
VIIA '~t ~

~ ~ ~ y~,~Me ~ ,~f_ o~Me o Mc ~, ~Me Az lX ~/ O~

_XO VDM-N~ 3 X~

~ Mc co_~l r~ ~___~ ~cbonc) ~X oli~
~, !

.~ ,. .
. .~
f~

:
, . .

. WOg 7012 PCTrUS91/~4 `' ' ,. ., "`' l~
Proton loss from the penultimate group is an important issue. VDM is the strongest base or proton acceptor in the system because its positively charged . conjugate acid can be stabilized by charge deloca}ization "~ 5 (not possible with other azlactones possessing saturated alkyl groups in the 2-position) in the following manner:

--~ U

-:~1 15 Me = methyl Continued oligomerlzation can continue from bo~h the remaining methine hydrogen of the original Michael adduct or from the two new methylene hydrogens in the newly added VDM.

Case 2: VDM Michael addition ... .

~c'~ .

, ~

- .. :.. . . : . . . :

' ~

' ?~
.`. . WO ~ 7012 PCr/USg~/0664 , ., : 2~2~03 ,9 .
.. ~ ~
,,, ~ VI
=\t N~b~e oligoo~zc e ~_NH M~

o b~uc ~ o~-~$
Mc M ~ O

~/ hiplinetr:
M/~Me (bu l~one) olig~s Mc ~O ~ ~ hl~h cy~ics hlgh he~lo-comalnin~ (b~e~
' oE~wDs ~r .:. ~
~5-', .,,, . .~ .
.

7? ',~' - ` . . , :1 , .. . . .
" ~ '' ' .
,, . ~ ~ ` ' . " ' . . ' ' ,., ~ .; ' . ~ ' ' ' ' ' ' . ~ ' ' '`
.

~ WO9~07012 PCT/US91/0~4 L~ ~ ~ 2 ~ ~ ~
,~o The initial Michael adduct can oligomerize in the manner of gegenions just described in case l or it can cyclize to form six- or eight-membered ring co~pounds which result from either C- (six-membered) or N- (eight-membered) Michael addition of the ketenaminal to the positively charged Michael adduct of the initial Michael addition.
Once this cyclization has occurred, additional oligomerization can take place from the ketenaminal portion and/or the enolizable methine (in the six-membered ring) portion of the ring structures.
An additional feature of Case 2 type oligomerizations is that the initial positively charged, ; alkylated VDM portion of the adduct may not persist over the course of oligomerization. Cyclization (either C- or N-) lS and loss of a proton can take place even at later stages of oligomerization to generate larger heterocycles as well, such as Formula VI when q is at least 2 or with Formula IX
compounds.
An important distinction between the oligomers of zO the present invention compared to the analogous syste~s mentioned in the background sectiOn is that the present oligomers are oligomerized predominantly through the 2-alkenyl groups, i.e., they consist of "vinyl units" as depicted earlier. In contrast, the oxazoline systems were either exclusively or predominantly (80%) polvmerized or oligomerized via "Michael units" created by N-Michael addition of the oxazoline ring nitrogen to the 2-alkenyl j group. Examination of the lH-NMR spectrum ~or oligo(VDM) in Figure 3A and integration of the resonances greater than 3 ppm reveals that at most lO % of the oligomeric products are comprised of Michael units.
Objects and advantages of this invention are further illustrated by the following examples, but the ~, particular materials and amounts thereof recited in these I -- 35 examples, as well as other conditions and details, should ; not be construed to unduly limit the invention. Examples l ~. , ~
~ .

' .' .

- 'WO92t07012 PCT/US91/~
.
9 2 ~

through 18 deal in general with important variations in the process of synthesizing oligo(2-alkenyl szlactones), Examples 19 through 28 deal with characterization, and ,~ Example 29 examines one utilization of the oligomeric products of the invention.

ExamDle This example teaches use of a Bronsted acid catalyst to effect the oligomerization of VDM.
VDM (350 grams; 2.517 moles), methyl ethyl ketone (MEK, 350 grams), 2,6-di-t-butyl-4-methylphenol (BBT, available from Aldrich Chemical Co., Milwaukee, WI, employed as a stabilizer to prevent any free radical polymerization) (0.70 gram), and trifluoroacetic acid (TFA, available from Aldrich Chemical Co.) (14.35 grams; 0.126 mole) were placed in a sealed glass bottle. The bottle was placed in an Atlas Launderometer (available from Atlas Electric Devices Co., Chicago, IL) at 60C for 22.5 hours. During the reaction time the initially colorless solution o~ reactants turned red in color. Progress of the oligomerization was measured by gas chromatography observing the disappearance of VDM
relative to the MEX solvent. Percent conversion to higher i molecular weight products was 97.8 %. Removal of the solvent in vacuo left an orange ~riable foamy product. The product was shown to be a multi-component mixture by hplc analysis, and a chromatogram is shown in FIG. 1. ~he solid azlactone-functional product was exposed to 70% relative humidity at 22C for 36 h during which the azlactone CzO at about 5.5 micrometers disappeared due to ring-opening hydrolysis. A sample was injected onto a 15 cm x 4 mm (id) ~amilton PRP [poly(styrene-co-divinylbenzene), available ~rom the Hamilton Co., Reno, NV] column and eluted with water acetonitrile mixtures also containing O.lS by volume trifluoroacetic acid. In the period from 0 to 45 minutes, the eluting solvent varied from water-acetonitile 90:10 to 60:40 mixtures; from 45 to 60 minutes the mixtures varied , ~ ~:
W092/0~012 PCTrUS91J~4 .... .
~2~03 from 60:40 to 20:80. Upper trace 10 represents components absorbing 210 nm incident ultraviolet light, while lower trace 12 represents those components absorbing 325 nm light and which manifest visible color.

-', These examples teach that useful Bronsted acids 1 possess pRa's of less than 1.2.
! The reactions to assess the activity of the various catalysts were conducted at 22C in ethyl acetate solvent (solvent weight ~raction 0.6) and using 5 mole percent of the catalyst. Percent conversions were ~, determined using the gas chromatography procedure of Example ', 1. The results are given in the following table:
. '! '~ 15 - Bronsted Acid % Conversion ~xam~le Catalyst DKa After 18 h 2 Perchloric -8 72 Acid 3 Trifluoro- 0.23 40 acetic Acid . ;!
s ~l 25 4 ~richloro- 0.66 40 - ' acetic Acid .,,.. ~ .
5~ Dichloro- 1.25 3 acetic Acid 6 Acetic Acid4.76 <1 ~, EXAMPLES 7-9 -- I 35 These examples teach that Lewis acidic materials can also be effective catalysts for promoting oligomerization.
: Reactions were conducted at 22C in ;l , .
acetonitrile (solvent weight fraction = 0.5) and using 5 ' 40 mole percent catalyst. Percent conversions were again determined using gas chromatography, and the results are given in the following table:
. -:

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~ W092/07012 PCTrUS91/~4 , ~ .
; 2~92~
Lewis Acid S Conversion Example Catalyst After 72 h ~ 7 Aluminum Z5 ; 5 Chloride ~" 8 Boron Trifluoride 78 Etherate 9 Zinc Chloride 21 This example teaches increased oligomerization rates can be achieved by increasing reaction temperature.
; Employing the procedure of Exa~ple 3, i.e., 40 wt ~ VDM in ethyl acetate, 5 mole percent TFA, and a 24 h reaction time, percent conversions were measured at three reaction temperatures. At -2C 22%, at 22C 43%, and at 59C 88% VDM had undergone oligomerization.

EXAMP~E 11 This example teaches that increasing catalyst concen~ration increases oligomerization rate.
Employing the procedure of Example 3 except that 0, 1.0, 5.Q, and 7.2 mole percent TFA concentration ; levels were employed, after 20 h the percsnt conversions i were 0, 1~, 42, and 59~, respectively.

These examples teach that increased oligomerization rates may be achieved by employing solvents of increased dielectric constants (e).
The examples shown in the table below were conducted using 0.5M concentrations of VDM in the various solvent mixtures, 5 mole percent TFA, and 7 days at 22C.
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W092/07012 PCT/VS91/n~4 2092~3 Z-~

MEX:Chloroform Examp~e Volume Ratio ~ % ConYersion - 12 100:0 18.5 57 ~: 5 13 75:25 15.1 56 14 50:50 11.6 51 25:75 8.2 45 16 0:100 4.7 36 This example teaches that 2-isopropenyl azlactones undergo oligomerization as well but generally require stronger acidic catalysts than their 2-vinyl azlactone counterparts.
2-Isopropenyl-4,4-dimethylazlactone (IDM) was synthesized by the method of Taylor et al., J. Polym. sci.
Polym. Lett., 9, 187 (1971). The procedure of Example 3 was employed except that IDM was utilized instead of VDM and ethanesulfonic acid (pXa = 0) instead of TFA. After 4 days at 22C, 20.1 % of the IDM had been oligomerized into higher molecular weight products; TFA was not as effective under the same conditions.

-' EXAMPLE ~8 This example teaches that six-membered ring 2-alkenyl azlactone compounds undergo oligomerization as well. 2-Vinyl-4,4-dimethyl-2-oxazin-6-one (VOX) was prepared by the method of Heilmann et al., J. Polvm. Sci.:
polym. Chem. d., 1984, 22, 1179.
The oligomerization was conducted by VOX in ethyl acetate (solvent weight fraction = 0.6) and using TFA
(5 mol %) as catalyst. The solutio~ was heated at 700C for 19 h. The conversion to oligomeric products was 25 %.

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` ~5 '~2~3 -~ EXAMPLE 19 This example teaches that the azlactone functional group remains intact after oligomerization.
-;s In FIG. 2 are presented three infrared spectra.
Spectrum 2A is of a film of oligo(VDM) prepared by the method of Example 3. Spectrum 2B is of a fil~ of poly(VDM) ' prepared in methyl ethyl ketone (MEX) at 31.3 ~ solids using I azobis(isobutyronitrile) ~AIBN) (0.5 wt %) as initiator at 600c for 18 h; the we~ght-average molecul~r weight ~3 determined by size exclusion chromatography was 135,000.
Spectrum 2C is of 2-ethyl-4,4-dimethylazlactone (EDM) prepared by the method of Rasmussen et al., J. Polym. Sci.:
, Polym. Chem. ~, 1986, 24, 2739.
? , . The oligo(VDM) is thus compared directly to two azlactones, one a mixture of high molecular weight polymers .~ and the other a pure low molecular weight compound, that contain saturated alkyl groups at position-2. The comparison of the carbonyl absorption peaks 14 in FIGS. 2A, 2B, and 2C at about 1820 cm~1, the carbon-nitrogen double bond stretching absorption peaks 16 at about 1675 cm~l, and two absorption peaks 18 and zo attributed to the azlactone heterocycle in the fingerprint region at about 965 and 895 cm~l shows that less than a 5 cm~1 variation exists among all three spectra at these intense absorption regions.

This example elaborates some of the differences in various spectra of poly~VDM) and oligo(VDM).
FIG. 3 shows the lH-MMR spectra of poly(VDM) (3B) and oligo(VDM) (3A). Noteworthy features in the spectrum of poly(VDM) are broadened resonances indicative of high molecular weight and the relative positions of backbone methine resonance 22 at 2.7 ppm and methylene resonances 24 at 1.6-2.2 ppm as shown in FIG. 3B. Resonances for oligo(VDM) are not nearly as broad, and fine structure, ~^. i.e., multiplets derived from coupling, is still evident .

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- WO92~07012 PCT/US91/0~4 which indicates lower molecular weight. In addition to many resonances in the expected range of resonances 26 from 1.6-2.7 ppm for methylene and methine, additional resonances 28 are observed downfield to about 4 ppm which may be attributed to methylenes/methines adjacent to heteroatoms or that are contained in relatively strained cyclic structures.
FIG. 4 shows the 13C-NMR spectra of poly(VDM) (4B) and oligo(VDM) (4A). The poly(VDM) spectrum is relatively straight forward wlth a gem-dimethyl carbon resonance 30 at 24 ppm, methylene and methine carbon resonances 32 between 32-36 ppm, the quaternary carbon resonance 34 at 65 ppm, the C=N resonance 36 at 163 ppm, and the C-O resonance 38 at 180 ppm. Oligo(VDM) is similar but with significant differences being observed in the methylenetmethine and C=N regions~ Also, resonances 40 at 116 and 113 may be indicative of minor amounts of olefinic carbons.
The W spectra of FIG. 5, perhaps more than the other spectroscopic methods, point out significant differences between oligo(VDM) (5A) and the conventional azlactones poly(VDM) (5B) and EDM (5c). The latter two azlactones exhibit essentially no absorption above 300 nm, ! while the oligo(VDM) material must contain at least a small number of chromophores involving extended, con~ugated systems to account ~or the significant absorption 42 above 300 nm (~x ' 331).

EXAMPLE ~1 This example teaches that the product of the acid-catalyzed reaction is comprised of relatively low molecular weight components.
In the absence of termination reactions and in systems in which the initiating species operates with unit efficiency, degree of polymerization or oligomerization (and -~! 35 ultimately number-average molecular weight) can be - .-- ~ . ..~ - ' ~, ' ' W092/07012 PCT/US91/~4 - ~ ` 2~92~03 ~.
calculated for addition polymers using the following relationship:

XN = rM1 f~j 5~I]
where XN = degree of polymerization or oligomèrization ~M~ = molar concentration of monomer tI~ = molar concentration of initiator It therefore follows that molecular weight in such systems should be quite sensitive to initiator concentration.
When the oligomerization of VDM was conducted in ethyl acetate (solvent weight fraction 0.6) with varying amounts of TFA initiator, however, molecular weight was shown to be quite insensitive to initiator concentration.
The data in the following table indicate that the molecular weight is very low compared to predicted values and remains quite constant regardless of initiator concentration.

_ Determined MN
Calculated ~Ea~ mol% - ~ -- GPCB Rast Cam~h -. 25 l.o 13 900 701 __ __ ... l _ ._ ..
2.0 6,950 770 __ 582 . .... .. _ ._ 4~0 3,475 806 794 _ 8.0 1,737 788 __ 572 .. _ .. _ ._ .. _, ._ ._ , .
.

A - All oligo(VDM) samples were further reacted with excess n-butylamine in order to generate non-reactive materials for characterization. The resulting ring-opened materials were twice precipitated into diethyl ether and dried under vacuum.
~, B Gel permeation chromatography (GPC) was conducted in tetrahydrofuran (THF) solution employing a series of ... . .
.,.-~i`~' . ' " ~-" ' ' - ' ~
:' ' , W092/07012 PCT/VS91/~4 . ,~.,- .
9 2 ~ 0 3 a8 Toyo Soda Manufacturing Co. columns (G3000, G2000, and G1000 available from Phenomenex, Rancho Palos Verde, CA), one microstyragel column (500 A available from Waters Chromatorgraphy Division, Milipore Corp., -~
Milford, MA), and one Waters microstyragel column ~100 A) repacked by Analytical Sciences, Inc. (Santa Clara, ~ CA). Molecular weights were determined by comparison ¦ to polystyrene standards.
C - The procedure utilized was that outlined in A.I. Vogel, ~ 10 "A Textbook of Practical Organic Chemistry," 3rd - Edition, ~ongman Group Limited: London, 1970, p. 1037.
D - Vapor Phase Osmometry (VPO) was conducted in THF
, solution by Arro Laboratory, Inc. (Joliet, IL).

`f' 15 ~XAMPLES 22-25 -` These examples demonstrate the variablity in distribution of oligomers depending on such factors as the nature of initiating acid and solvent.
The examples in the table below were all conducted at 22C using 5 mole percent of the initiating acid and a solvent welght fraction of 0.5.
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-~ 1 Example CatalystSolvent GPC Peak MW
. __ ~:1 22 TFAnitrile~IG. 6A 718 (44) l _ . __. .. _ . ll - ~ 25 23 TFAaceticFIG. 6B 1001 (46) j l acid .-.. ! 24 ethanesul- aceto- FIG. 6C 853 (48) fonic acid nitrile - _ _ 25sulfuric aceto- FIG. 6D 257 (50) acid nitrile _ 502 (52) "
~ .
These size exclusion chromatograms reveal that the majority of products has molecular weights of less than 2000, although a small amount of intermediate molecular weight -~ products, ca. 20,000, is produced in some instances.

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This example provides specific evidence for oligomers possessing degrees of oligomerization of up to nine.
The oligomer of Example 25 was poured into a crystallizing dish and allowed to air dry (at 70 % relative humidity) for 24 hours. IR analysis indicated that the azlactone carbonyl absorption had disappeared. The partially hydrolyzed oligomer was dissolved in dithiothreitol and examined by Fast Atom Bombardm~nt (FAB) Mass Spectrometry. Among other peaks in the spectrum were the following with possible assignments:

m/e Possib~e Assianment*
611 4(VDM) + 3 waters + 1 768 5(VDM) ~ 4 waters + 1 925 6(VDM) + 5 waters + 1 1082 7(VDM) + 6 waters + 1 1239 8(VDM) + 7 waters + 1 1396 9(VDM) + 8 waters + 1 * - where, for example, 4 (VDM) + 3 waters + 1 indicates a chemically protonated tetramer wherein 3 of the azlactone rings have been ring-opened with water, i.e.
hydrolyzed;
m/e ~ masstcharge 1`- .

- This example teaches that hydrogens on carbons ad~acent to azlactone rings are labile and can be substituted by 2-alkenyl azlactone residues.
A solution containing deuterochloroform (3.94 ~ grams), EDM (1.41 grams; 0.01 mole), and TFA ~1.25 grams;
`^ 0.011 mole) was prepared and cooled to -7BC. VDM (1.39 -i 35 grams; 0.01 mole) was added in a stream without incident.
Upon warming to room temperature, the solution became yellow . ,~,.
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and slightly viscous. After 3 days at 22-C, the lH-NMR
contained in addition to a normal oligo(VDM) spectrum a doublet centered at 1.34 ppm (relative to tetramethylsilane) -~ indicative of the -C~CH3- group of the incorporated EDM;
integration revealed that 31 S of the EDM charged was incorporated. GC-MS analysis employing electron impact revealed the presence of an EDM:VDM dimer (m/e = 280). This result indicated that methylene hydrogens adjacent to an azlactone group are able to participate in the ' 10 oligomerization reaction.
SimilArly, 2-isopropyl-4,4-dimethylazlactone prepared by the method of Rasmussen et al-, ~. PO~Y~
Polvm. Chem~ Ed., 1986, 24, 2739 (b.p. - 91-92-C at 60 Torr.) was subjected to the same reaction conditions as the EDM above. A gem-dimethyl resonance for the incorporated 2-isopropyl material was observed in the lH-NMR as a singlet at 1.34 ppm. GC-MS analysis showed a molecular ion for the 1:1 adduct with VDM at m/e = 294. The data of this Example show that methine hydrogens ad~acent to azlactone groups may also participate in the oligomerization reaction.
~E~
This example teaches that oligomerization occurs only with ~ mmonium ion generating agente that can be readily 1,3-shifted, such as a proton or other Lewis ~cid.
In this trial a methyl group was utilized as a i non-removable immonium ion generating agent. The ¦ oligomerization of VDM was examined in acetonitrile solution (solvent weight fraction 0.6) at 22C by adding ~.2, 16.4, and 49.2 mol % (based on VDM) of methyl p-toluenesulfonate.
After 96 h, the reactions were examined by gas chromatography, and the corresponding amounts of VDM that were unaccounted for were 7.8, 16.5, and 44.1 mole %, - respectively. Thus, although the methylating agent did - 35 apparently form the immonium ion by reaction with VDM
accounting for the 1:1 correspondence in methylating agent `', :' ' .
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WO 92/07012 PCr/1~59llO4644 9 2 ~ 0 3 .
charged to undetected VDM, VDM does not react, i.e., undergo oligomerization, with the VDM-Met i~monium ion. A possible rationale is that Michael ~ddition of VDM to YDM-Me' creates an unstable ketenaminal that cannot undergo stabilization by a 1,3-shift as is possible with the acid catalysts of the - ~nvention.

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Me ~ Me ' ~ Mc ,~ . i. O

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E~a~PL~ 29 This example teaches utilization of oligo~VDM) as a crosslinker for a pressure sensitive adhesive.
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~ ~07012 PCTtUS91/0~4 . , ~ . .
` ~Z 2~92403 Preparation of CopolytIso-octyl Acrylate:
N-Vinylpyrrolidinone:~ydroxyethyl Methacrylate (88:8:4 w/wtw)]
,~ The following ingredients were charged into a glass bottle:
Iso-octyl Acrylate (IOA) 66.0 grams N-Vinylpyrrolidinone (NVP) 6.0 grams Hydroxyethyl Methacrylate (HEMA!) 3.0 grams MEK 75.0 grams 10AIBN 0.15 gram The resulting solution was deoxygenated using a nitrogen sparge, sealed, and heated at 55C for 24 h in a launderometer. Conversion to copolymer was 98.8 % as measured gravimetrically after volatilization of solvent and unreacted monomers.

Evaluation of Oligo(VDM) as a Crosslinker The resulting copolymer solution was diluted to 33 % solids by addition of more MEK. Two coating solutions were prepared: l) a control containing no oligo(V~M) and 2) the test sample which contained oligo(VDM) prepared as in Example 3 in equal molar amount as the HEMA in the adhesive and ethanesulfonic acid t3 mol %, based on oligo(VDM)]. The solutions were knife-coated onto polyester ~ilm (0.05 mm) to a thickness of about 0.25 mm and dried in an air-circulating oven at 100C for 10 minutes to remove solvent and effect crosslinking; dry coating weights were about 64 g/m2.
Cohesive strengths of the resultant pressure sensitive tapes were compared by means of a standard shear strength test (Interim Federal Test Method Standard No. 147, March 12, 1963), in which a 500 gram load was suspended from an ~dhesive contact area of 6.4 cm2, and the time required for the tape to separate from the stéel plate was measured and recorded in minutes as the average of three trials. The ~-~' results are given in the following table:

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WO 9~/07012 PCr/US91tO6644 . ~ .
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Sample Shear ~miny~esl Control 24 . 7 Test 47.7 ~.,,,~
The data of this Example show the oligo(VDM)-containing formulation possessed a significantly increased cohesive strength relative to the control.
1, Various modlfications and alterations o~ this invention will become apparent to those skilled in tbe art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

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Claims (10)

Claims:

1. An azlactone-functional oligomer of a 2-alkenyl-4,4-disubstituted azlactone having 2 to 15 units of which at least 30 mole percent are 2-alkenyl group polymerized units.

2. The oligomer according to claim 1 being selected from A, B, and C wherein:

A is an oligomer having the formula:

VI

wherein R1 and R2 independently represent an alkyl group of 1 to 14 carbon atoms, a cycloalkyl group of 3 to 12 carbon atoms, an aryl group of 5 to 12 ring atoms, or R1 and R2 taken together with the carbon atom to which they are joined form a carbocyclic ring of 4 to 12 ring atoms;
R3 and R4 are independently hydrogen or lower alkyl;
n is 0 or 1;
Az is a symbol for 2-bonded azlactone group in which R1, R2, R3, R4, and n are as defined above:

G independently can be hydrogen, methyl, and groups selected from -CH2CHGAz, -CH2CG(Az)CH2CHGAz, and -CH2CG(Az)[CH2CG(Az)]pCH2CGAz, wherein p can have integral values from 0 to about 12, with the proviso that the extent of oligomerization in G does not exceed a total number-average molecular weight of about 2000 for the oligomers depicted by Formula VI;
r can be 0 or 1; and q can have integral values from 1 to about 12;
B is an oligomer having the formulae:

or VIIA VIIB
wherein Az and G are as defined above, with the proviso that in Formula VIIA at most one G can be hydrogen or methyl, and in Formula VIIB G cannot be hydrogen or methyl; and X is the covalently bonded counter ion or gegenion of a Bronsted acid whose pKa is less than 1.2, or X can be a 3-quaternized 2-alkenyl azlactone group of formula VIII

in which R5 is hydrogen or methyl and all other symbols are as previously defined;

VIII

C is an oligomer having the formula IX

wherein Az, G and q are as previously defined.

3. The oligomer according to claims 1 and 2 having a number average molecular weight in the range of about 278 to 2000.

4. The oligomer according to claims 1 to 3 wherein said oligomer has at least 30 mole percent carbon-carbon backbone segments.

5. A method for preparing the oligomer according to claims 1 to 4 comprising the steps:
oligomerizing at least one 2-alkenyl azlactone in the presence of a catalytically effective amount of an acid to provide an oligomer having 2 to 15 units which are predominantly 2-alkenyl group polymerized units.

6. The method according to claim 5 wherein said acid is a Bronsted or Lewis acid.

7. The method according to claim 6 wherein said Bronsted acid has a pKa of less than 1.2.

8. The method according to claims 6 and 7 wherein said Bronsted acid is selected from the group consisting of:
sulfuric acid, hydrogen chloride, hydrogen bromide, hydrogen iodide, trifluoroacetic acid, trichloroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, perchloric acid, and ethanesulfonic acid; or said Lewis acid is selected from the group consisting of:
aluminum chloride, zinc chloride, boron trifluoride, antimony pentachloride, titanium tetrachloride and iodine.

9. The method according to claims 5 to 8 wherein said 2-alkenyl azlactone is selected from the group consisting of:
2-vinyl-4,4-dimethyl-2-oxazolin-5-one, 2-isopropenyl-4,4-dimethyl-2-oxazolin-5-one, 2-vinyl-4-ethyl-4-methyl-2-oxazolin-5-one, 2-vinyl-4,4-dimethyl-1,3-oxazin-6-one.

10. The method according to claims 5 to 9 wherein said 2-alkenyl azlactone is 2-vinyl-4,4-dimethyl azlactone.