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Phase behavior for blends of styrene containing triblock copolymers with poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Author(s) -
Tucker P. S.,
Barlow J. W.,
Paul D. R.
Publication year - 1987
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1987.070340504
Subject(s) - copolymer , materials science , polystyrene , styrene , polymer chemistry , phase (matter) , phenylene , differential scanning calorimetry , glass transition , oxide , ethylene oxide , chemical engineering , polymer , composite material , organic chemistry , chemistry , thermodynamics , physics , metallurgy , engineering
Abstract The extent to which the styrene end‐blocks of three commercially available triblock copolymers can mix with a particular poly(2,6‐dimethyl‐1,4‐phenylene oxide) ( M n = 22,600 and M w = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene‐based mid‐block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene‐based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid‐block) exhibited single composition‐dependent T g s for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid‐block exhibited two separate hard phase T g s corresponding to an essentially pure PPO phase and a PS‐rich phase. For blends of homopolymer PS with styrene‐based block copolymers, the similar two‐phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.