TY - JOUR
T1 - Synthesis and characterization of elastomeric heptablock terpolymers structured by crystallization
AU - Alfonzo, C. Guillermo
AU - Fleury, Guillaume
AU - Chaffin, Kimberly A.
AU - Bates, Frank S.
PY - 2010/6/22
Y1 - 2010/6/22
N2 - We report the synthesis and characterization of fully saturated hydrocarbon block copolymer thermoplastic elastomers with competitive mechanical properties and attractive processing features. Block copolymers containing glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were produced in a CEC - P - CEC heptablock architecture, denoted XPX, by anionic polymerization and catalytic hydrogenation. The X blocks contain equal volume fractions of C and E, totaling 40% - 60% of the material overall. All the XPX polymers are disordered above the melt temperature for E (Tm,E - 95 °C) as evidenced by SAXS and dynamic mechanical spectroscopy measurements. Cooling below Tm,E results in crystallization of the E blocks, which induces microphase segregation of E, C, and P into a complex morphology with a continuous rubbery domain and randomly arranged hard domains as shown by TEM. This mechanism of segregation decouples the processing temperature from the XPX molecular weight up to a limiting value. Tensile mechanical testing (simple extension and cyclic loading) demonstrates that the tensile strength (ca. 30 MPa) and strain at break (>500%) are comparable to the behavior of CPC triblock thermoplastic elastomers of similar molecular weight and glass content. However, in the CPC materials, processability is constrained by the order - disorder transition temperature, limiting the applications of these materials. Elastic recovery of the XPX materials following seven cycles of tensile deformation is correlated with the fraction of X in the heptablock copolymer, and the residual strain approaches that of CPC when the fraction of hard blocks fX = 0.39.
AB - We report the synthesis and characterization of fully saturated hydrocarbon block copolymer thermoplastic elastomers with competitive mechanical properties and attractive processing features. Block copolymers containing glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were produced in a CEC - P - CEC heptablock architecture, denoted XPX, by anionic polymerization and catalytic hydrogenation. The X blocks contain equal volume fractions of C and E, totaling 40% - 60% of the material overall. All the XPX polymers are disordered above the melt temperature for E (Tm,E - 95 °C) as evidenced by SAXS and dynamic mechanical spectroscopy measurements. Cooling below Tm,E results in crystallization of the E blocks, which induces microphase segregation of E, C, and P into a complex morphology with a continuous rubbery domain and randomly arranged hard domains as shown by TEM. This mechanism of segregation decouples the processing temperature from the XPX molecular weight up to a limiting value. Tensile mechanical testing (simple extension and cyclic loading) demonstrates that the tensile strength (ca. 30 MPa) and strain at break (>500%) are comparable to the behavior of CPC triblock thermoplastic elastomers of similar molecular weight and glass content. However, in the CPC materials, processability is constrained by the order - disorder transition temperature, limiting the applications of these materials. Elastic recovery of the XPX materials following seven cycles of tensile deformation is correlated with the fraction of X in the heptablock copolymer, and the residual strain approaches that of CPC when the fraction of hard blocks fX = 0.39.
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U2 - 10.1021/ma100347k
DO - 10.1021/ma100347k
M3 - Article
AN - SCOPUS:77953655957
SN - 0024-9297
VL - 43
SP - 5295
EP - 5305
JO - Macromolecules
JF - Macromolecules
IS - 12
ER -