TY - JOUR
T1 - ABA triblock copolymers containing polyhedral oligomeric silsesquioxane pendant groups
T2 - Synthesis and unique properties
AU - Pyun, Jeffrey
AU - Matyjaszewski, Krzysztof
AU - Wu, Jian
AU - Kim, Gyeong Man
AU - Chun, Seung B.
AU - Mather, Patrick T.
N1 - Funding Information:
PTM acknowledges preliminary WAXS analysis performed by Dr Hong G. Jeon and financial support of AFOSR, Grant F49620-00-1-0100. The National Science Foundation under Grant No. PHY99-07949 (PTM), DMR 9871450 (KM) and Dr John Harrison, Legacy Fellowship at GMU, (JP) are gratefully acknowledged for funding of this research.
PY - 2003/3/31
Y1 - 2003/3/31
N2 - The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly (3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.1 3,9.15,15.17,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP = 6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase- separated material exhibits a tensile modulus larger than expected (ca. 2 × 108 Pa) for a continuous rubber phase for temperatures between a pBA-related Tg and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the Tg of the higher Tg phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The Tg of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of Tg in this system.
AB - The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly (3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.1 3,9.15,15.17,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP = 6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase- separated material exhibits a tensile modulus larger than expected (ca. 2 × 108 Pa) for a continuous rubber phase for temperatures between a pBA-related Tg and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the Tg of the higher Tg phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The Tg of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of Tg in this system.
KW - Block copolymers
KW - POSS
KW - Polyhedral oligomeric silsesquioxane
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U2 - 10.1016/S0032-3861(03)00027-2
DO - 10.1016/S0032-3861(03)00027-2
M3 - Article
AN - SCOPUS:0037474750
SN - 0032-3861
VL - 44
SP - 2739
EP - 2750
JO - Polymer
JF - Polymer
IS - 9
ER -