Thiepan-2-one (dhiocaprolactone) was prepared by cyclization of 6-mercaptohexanoic acid and polymerized by a base-catalyzed ring-opening reaction to a linear poly(thio1 ester). Poly-e-thiocaprolactone is crystalline and has a high molecular weight (intrinsic viscosity, 0.5-1 .O dl/g in chloroform. Its crystalline melting point is 105"; it has a second-order transition at +19" and is soluble in several common solyents, especially in partially halogenated hydrocarbons, When oriented by drawing, it has a fiber period of 17.8 A, which corresponds to the length of two extended thiol ester repeat units (14 atoms in the backbone). Thian-2-one (6-thiovalerolactone) can also be converted to a crystalline polymer, but thiolan-2-one (y-thiobutyrolactone) does not react under these conditions. The reactivity of the thiolactones toward polymerization catalysts is, therefore, dependent on ring size in a manner which is analogous to the behavior of lactones but which is different from that of lactams.hiolan-2-one (y-thiobutyrolactone, I)3 and thian-2-

Poly(viny1amine) is a water-soluble polymer of considerable potential application. The polymer is prepared by solution polymerization of N-vinyl-t-butylcarbamate' or N-vinylacetamide2 followed by hydrolysis. The poly(viny1amine) prepared from Nvinyl-t-butylcarbamate was reported to be predominantly syndiotactic? However, a recent study indicates that it is probably a t a~t i c . ~~~ We are interested in the preparation of a more stereoregular poly(viny1amine). N-Vinyl-t-butylcarbamate can be purified by sublimation. It has a highly crystalline form. We anticipate that solid state polymerization of the crystalline monomer will produce a polymer with a different tacticity from that prepared by solution polymerization.Most solid state polymerizations are initiated by high-energy radiation, e.g., y-or x-rays, or ultraviolet light!,'The solid state suspension polymerization of N-vinylcarbazole by a redox catalyst was reported by Okamura?yg However, only a low molecular weight polymer ( T~~,~ = 0.04-0.07, C = 1, 3OOC) was obtained. Here we report the solid state suspension polymerization of N-vinyl-t-butylcarbamate. The monomer, N-vinyl-t-butylcarbamate is water-insoluble. With this technique, the crystalline monomer is suspended on the surface of the water. After a surfactant is added to the system, the monomer crystals are immersed in the aqueous system thereby allowing good contact with the water. A water-soluble initiator is used to catalyze the polymerization.'o An alternative procedure has also been used: nitrogen gas is bubbled through the solution to achieve contact between the crystals and the solution during polymerization." Polymerization occurs when a water-soluble azo initiation, 2,2'azobis(N,N'-dimethyleneisobutyramidine) dihydrochloride is used. However, only crosslinked material is obtained. The crosslinked material appears to have the same shape as the original monomer particles.Interesting results are obtained when N-hydroxysuccinimide is added to the system; in this case, polymerization occurs without crosslinking. The monomer particle breaks into s m d units and has a cloudy appearance. The inherent viscosity and the crystallizability of the polymers are dependent on the amount of N-hydroxysuccinimide (HOSu) in the system. As indicated in Table I, when large amounts of HOSu are added, the polymers are crystalline. However, the viscosity was low. When smaller amounts of HOSu are used, the polymers (2, 3, 4, 5 ) have a higher viscosity and are also crystallizable. The crystallized polymer 5 has a high degree of crystallinity as reflected by its x-ray powder diffraction pattern (Fig. 1). When a very small amount of HOSu is used, the viscosity of the polymer ( 6 ) is high. However, the polymer does not crystallize from acetone. The atactic poly(N-vinyl-t-butylcarbamate) (PNVTBC) prepared by solution polymerization does not crystallize from acetone. Table I1 demonstrates the effect of HOSu on viscosity and crosslinking of the polymers. Polymer 7 shows a higher viscosity than does polymer 6.

The utilization of synthetic macromolecules to change the reactivities of low molecular weight species has recently received considerable attention,2 particularly since these reactions can serve as models for the

For the purpose of preparing polymeric model enzyme systems, 4( 5)-vinylimidazole was synthesized by two Attempts to dehydrochlorinate The polymerization and copolymerization of this monomer, to routes, one starting with histidine, and the other with 2-butyne-1,4-diol. 4(2'-chloroethy1)-imidazole were unsuccessful, give polymers containing pendant imidazole, hydroxyl and carboxyl groups, is described.

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