NMR studies of structural phase transitions in random copolymers

被引：3

作者：

McCormick, M

Reimer, JRA

机构：

[1] Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA

[2] Univ Calif Berkeley, Dept Chem Engn, Berkeley, CA 94720 USA

来源：

MACROMOLECULES | 2003年 / 36卷 / 02期

关键词：

D O I：

10.1021/ma021433k

中图分类号：

O63 [高分子化学（高聚物）];

学科分类号：

070305 ; 080501 ; 081704 ;

摘要：

Nuclear magnetic resonance (NMR) has been used in conjunction with circular dichroism (CD) and intrinsic viscosity (IV) measurements to probe the phase diagram of poly(L-glutamic acid-ran-L-leucine) (PEL). IV measurements indicate that PEL in aqueous salt solution undergoes a pH-mediated collapsing transition whereby its size decreases by a factor of 2.6 as the pH is decreased from 6.82 to 4.92. CD measurements indicate a pH-mediated helix-coil transition as the pH is increased from less than 5 to greater than 7. NMR relaxation times and nuclear Overhauser effects were obtained as a function of temperature for various phases of the PEL system and analyzed according to various models for polymer dynamics. The results of these analyses are discussed in the context of freezing transitions predicted by contemporary theories of random copolymers.

引用

页码：477 / 485

页数：9

共 31 条

[1] DETERMINATION OF ROTATIONAL MOBILITIES OF BACKBONE AND SIDE-CHAIN CARBONS OF POLY(GAMMA-BENZYL L-GLUTAMATE) IN HELICAL AND RANDOM-COIL STATES FROM MEASUREMENTS OF C-13 RELAXATION-TIMES AND NUCLEAR OVERHAUSER ENHANCEMENTS [J].