ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The ABA type block copolymer of 2-hydroxyethyl methacrylate (HEMA) and styrene was synthesized and the influence of the interaction between constituent blocks on the conformational change of the block copolymer was investigated in mixtures of DMF and 1,4-dioxane which are selective solvents for poly(HEMA) and polystyrene, respectively. The intrinsic viscosity [η] of the mixture from the parent homopolymers of the block copolymer was compared with the value calculated on assuming lack of interaction between unlike segments. The [η] value at 15°C was found to agree with the calculated value despite of incompatibility between dissimilar segments. On the contrary, the [η] value at 30°C deviated positively from the theoretical value, especially in N,N-dimethylformamide (DMF) or 1,4-dioxane-rich solvents, indicating that hetero contact between unlike segments at elevated temperature results in an increase of the average hydrodynamic volume because of repulsive interaction. The molecular expansion was found to become large with an enhancement of incompatibility. The same kind of transition versus temperature was observed in the intrinsic viscosity curve of the block copolymer, suggesting that hetero contacts between dissimilar segments occur at elevated temperature and that enhancement of solvent selectivity results in a conformational change of the block copolymer. A further increase of the solvent selectivity toward the polystyrene blocks was found to lead to intermolecular association of the block copolymer through aggregation of the poly(HEMA) side blocks.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1981.021820716
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