Effect of primary polymer chain rigidity on intramolecular cyclization and intramolecular crosslinking in free-radical crosslinking monomethacrylate/dimethacrylate copolymerizations

✍ Scribed by Jun-ichi Ikeda; Yasuhide Hasei; Yuduri Yasuda; Hiroyuki Aota; Akira Matsumoto

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 120 KB
• Volume: 94
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.20976

✦ Synopsis

Abstract

d‐Bornyl methacrylate (BoMA) was chosen as a typical example of bulky monomethacrylate monomers, the polymerization of which led to the formation of a rigid polymer chain. To discuss the effect of primary polymer chain rigidity on intramolecular cyclization, we compared the solution copolymerization results of BoMA with 1 mol % ethylene dimethacrylate (EDMA; n = 1) and poly(ethylene glycol dimethacrylate) [CH~2~C(CH~3~)CO(OCH~2~CH~2~)~n~OCOC(CH~3~)CH~2~, n = 9 (PEGDMA‐9)] with those of methyl methacrylate (MMA) with 1 mol % EDMA and PEGDMA‐9; the dependence of the weight‐average degree of polymerization on conversion for the former BoMA copolymerization systems was completely opposed to that for the latter MMA systems, and this was a reflection of a reduced occurrence of intramolecular cyclization caused by the rigidity of the primary polymer chain. The effect of primary polymer chain rigidity on intramolecular crosslinking was discussed through a comparison of both BoMA/EDMA and MMA/EDMA copolymerizations. The correlations of the intrinsic viscosity, root‐mean‐square (rms) radius of gyration, and second virial coefficient with the molecular weight were examined for both BoMA/EDMA (90/10) and MMA/EDMA (90/10) copolymerizations in a dilute solution because microgelation was observed in solution MMA/EDMA (90/10) copolymerization as a reflection of a locally extensive occurrence of intramolecular crosslinking. The logarithmic plots of both the intrinsic viscosity and rms radius of gyration versus the molecular weight for MMA/EDMA copolymerization were compared with those for the corresponding BoMA/EDMA copolymerizations. The second virial coefficients were greater than 10^−5^ mol cm^3^ g^−2^ for BoMA/EDMA copolymers, even when the conversion was very close to the gel point, whereas they were quite low, that is, less than 10^−5^ mol cm^3^ g^−2^, for an MMA/EDMA copolymer obtained at more than 15% conversion. These were ascribed to a suppressed occurrence of intramolecular crosslinking, a reflection of the lessened flexibility of the polymer main chain and a steric effect due to the bulky d‐bornyl groups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1086–1093, 2004