Calcium carbonate crystal growth on a chitosan substrate was achieved using a supersaturated calcium carbonate solution. Heterogeneous nucleation of the calcium carbonate crystals was significantly influenced by the chitosan surface profile. Poly(acrylic acid) (MW = 2000, PAA2K) was chosen to modify chitosan surfaces in aqueous solution. The adsorption of PAA2K occurred on the chitosan film surface. The thicknesses of the adsorbed chitosan films were determined by ellipsometry. X-ray photoelectron spectroscopy (XPS) was used to determine the surface structure of the modified chitosan films. Calcium carbonate crystal sizes and morphology were observed under a polarized optical microscope and a scanning electron microscope (SEM). PAA2K promoted the heterogeneous nucleation of calcium carbonate crystals on the chitosan film and at the same time suppressed homogeneous nucleation in solution.

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Polymerization of (4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate (MAPDST), as a key monomer containing the radiation sensitive sulfonium functionality, with various other monomers such as methyl methacrylate (MMA), 4-carboxy styrene (STYCOOH), N-vinyl carbazole (NVK) in different molar ratios via free-radical polymerization method is described. This methodology led to the development of a small chemical library of six different radiation sensitive polymers for lithography applications. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy identified the reaction products as MAPDST homopolymer and MAPDST-MMA, MAPDST-STYCOOH, MAPDST-NVK copolymers. Molecular weights were obtained from gel permeation chromatography and the decomposition temperature (Td) values were determined using thermogravimetric analysis (TGA). The effect of extreme ultraviolet (EUV) irradiation on a thin poly(MAPDST) film was investigated using monochromatic synchrotron excitation. These new polymeric materials were also exposed to electron-beam lithography (EBL) and extreme ultraviolet lithography (EUVL) to achieve 20-nm line patterns.

Introduction.Aliphatic polyesters are an important class of biodegradable and hydrolyzable synthetic polymers.'" A series of a-hydroxypolyesters, such as poly-(glycolic acid) (PGA), poly(1actic acid) (PLA), and their copolymers, have been successfully used as bioabsorbable sutures and surgical implants.lt3 Other types of polyesters,415 such as poly(caprolactone), poly(@-propiolactone), and poly(butyrolactone), can also be potentially used as biodegradable polymers in drug delivery and agricultural uses.On the other hand, commercial aliphatic polyamides (nylon 6 and nylon 66) are nonbiodegradable. The large concentration of hydrogen bonds and the high regularity of the polyamide structure are the possible reasons for the inertness of these nylons to biodegradation. On the basis of the above facts, poly(ester-amides) (PEAS) composed of esters and amides could potentially be a class of biodegradable polymers which would have better physical properties than polyesters.6-11Recently, aliphatic poly(ester-amides) containing ahydroxy or a-amino acid moieties have been studied for their potential biomedical applications. Helder and coworkers6 studied the in vitro degradation of nonalternating glycine/DL-lactic acid copolymers. Barrows and cow o r k e r~~~~ also synthesized a series of alternating poly-(ester-amides) by using a two-step polycondensation reaction from glycolic acid, diamine, and diacoyl chloride and investigated the in vivo degradation of the copolymers for the purpose of developing new surgical implants. However, very few studies on the degradation of poly-(ester-amides) have been reported. Tokiwa et al. 9JO showed that poly(ester-amides), made by amide-ester interchange reactions of nylons and polycaprolactone, were degraded by lipase. To develop degradable materials for general applications, two types of nonalternating PEAS were synthesized by anionic" and interfacial12 polymerizations. The hydrolysis (in buffer solution) and biodegradation (under attack of fungi) of these polymers were studied.Experimental Section. Nylon 6 was obtained from Polysciences Inc. and low-density polyethylene (LDPE) from Union Carbide (No. 6201). 1,6-Hexanediamine was purified by vacuum sublimation. t-Caprolactone, l,&hex-anediol, and adipoyl chloride were distilled at reduced pressure. e-Caprolactam was recrystallized from reagentgrade acetone three times and dried in vacuum. Alcoholfree chloroform was prepared by washing with distilled water three times, followed by drying with anhydrous CaClz and distillation. Dry methanol was prepared from absolute-grade methanol by drying with potassium methoxide followed by distillation. The catalyst, sodiocaprolactam, was made by reacting e-caprolactam with sodium methoxide in anhydrous methanol under argon. Excess methanol was distilled off and the residue heated under reduced pressure at 120-130 OC for 2 h to remove any remaining methanol and lactam.The intrinsic viscosities of the polymers were measured in a 0.5 g/dL solution of 90% formic acid at 25 "C. The infrared spectra of th...