Chain flexibility and glass transition temperatures of poly(n-alkyl (meth) acrylate)s: Implications of tacticity and chain dynamics

POLYMER

卷:213

Article

Li, Tianyu¹  Li, Hui⁵  Wang, Huiqun²  Lu, Wei²  Osa, Masashi⁴  Wang, Yangyang⁵  Mays, Jimmy²  Hong, Kunlun^3,5 

[1] Dept Mat Sci & Engn, Knoxville, TN 37996 USA

[2] Dept Chem, Knoxville, TN 37996 USA

[3] Univ Tennessee, Dept Chem & Biomol Engn, Knoxville, TN 37996 USA

[4] Aichi Univ Educ, Dept Chem, Kariya, Aichi 4488542, Japan

[5] Oak Ridge Natl Lab, Ctr Nanophase Mat Sci, Oak Ridge, TN 37831 USA

关键词: Poly(n-alkyl acrylate);    poly(n-alkyl methacrylate);    Tacticity;    Glass transition temperature;    Characteristic ratio;    Persistence length;    Chain flexibility;    Solution properties;   

DOI  :  10.1016/j.polymer.2020.123207

来源: Elsevier

【 摘 要 】

The relationship between chain microstructure and glass transition temperature (T-g) is complicated for poly (alkyl methacrylate)s and poly(alkyl acrylate)s. Despite intensive studies, relationships between the structures of these polymers and their properties, including solution characteristics and T-g, are still controversial. Solution properties, chain conformations, including Flory's characteristic ratio (C-infinity), persistence length (l(p)), and chain diameters, and T-g are reported for series of poly(n-alkyl acrylate)s and poly(n-alkyl methacrylate)s having alkyl side chain lengths (n) ranging from 1 to 10 carbons in length, with uniform and well-characterized tacticities. Chain flexibilities of both series of polymers decrease as n increases, reflecting increased hindrances to rotation about backbone bonds as side chains become longer. Conversely, the T(g)s for both series of polymers decrease substantially as n increases, reflecting the greater side chain mobilities of long alkyl substituents. For shorter alkyl chain lengths, T(g)s for the poly(n-alkyl acrylate)s are much lower than for the corresponding poly(n-alkyl methacrylate)s, a difference which has been attributed in the past to the presumed reduced chain flexibility of polymethacrylates due to the presence of the a-methyl substituent. However, contrary to such expectations, C-infinity, and l(p) values for these two series of polymers are nearly identical at a given n value, except for the longest n-alkyl substituents. Instead, the differences in T-g may be attributed to the differences in tacticity of the two series - almost ideally atactic for the poly(n-alkyl acrylate)s but high in syndiotacticity for the poly(n-alkyl methacrylate) s. The T(g)s for the two series of polymers approach that of polyethylene at longer alkyl chain lengths. In addition, the effects of tacticity and chain dynamics on C-infinity, l(p) , and T-g of poly(methyl methacrylate) is discussed.

【 授权许可】

Free