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Temperature‐induced Molecular Chain Motions of Styrenic Triblock Copolymers Studied by Intrinsic Fluorescence Spectra
Author(s) -
Yuan Zhongke,
Yang Dacheng,
Fan Li
Publication year - 2011
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201180376
Subject(s) - excimer , chemistry , polystyrene , copolymer , differential scanning calorimetry , fluorescence , melting point , monomer , glass transition , block (permutation group theory) , polymer chemistry , polymer , analytical chemistry (journal) , thermodynamics , organic chemistry , optics , physics , geometry , mathematics
The temperature‐induced molecular chain motions of styrenic triblock copolymers (SBC), i.e . polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) and polystyrene‐block‐poly(ethylene‐ co ‐1‐butene)‐block‐polystyrene (SEBS), were studied by intrinsic fluorescence method. For SBS, the glass transition temperatures ( T g s) of B block and S block obtained by intrinsic fluorescence method were in good agreement with differential scanning calorimetry measurements (DSC). In the case of SEBS, an isoemission point was observed at about 310 nm at elevated temperatures, suggesting the slight conversion between the monomer and excimer emission. On this basis, the molecular chain motion of SEBS was monitored by both fluorescence intensity and excimer/monomer fluorescence ratio. Besides the T g s of S block and EB blocks, a melting point ( T m ) of weak crystalline in EB block was unambiguously determined by intrinsic fluorescence. Furthermore, it was found that the melting process directly led to the slight loosening of PS segments in interface and consequently the reduction of the amount of excimer. A reasonable mechanism was proposed to describe the molecular chain movements and phase transitions of SEBS upon heating. Moreover, the influence of temperature on the apparent activation energy of non‐radiative process ( E a T ) around T g of S block was much stronger than that around T g of B or EB blocks.