Blends of Amorphous-Crystalline Block Copolymers with Amorphous Homopolymers. 2. Synthesis and Characterization of Poly(ethylene-propylene) Diblock Copolymer and Crystallization Kinetics for the Blend with Atactic Polypropylene

Abstract

A symmetric diblock ethylene-propylene copolymer (DEP) was synthesized through hydrogenation of an anionically polymerized polybutadiene-poly(2-methyl-1,3-pentadiene) diblock copolymer (PBDb-PMPD). IR and NMR measurements showed the hydrogenation to be more than 98% complete. The resultant diblock copolymer consists of an atactic polypropylene block and a polyethylene block (b-PE) containing 3 mol % of ethyl branches. Differential scanning calorimetry (DSC) was carried out for three series of binary blends made from DEP (Mw = 113 x 103) and three atactic polypropylene (APP) samples with molecular weights of MW = 15,39, and 190 X 103. Blending did not affect the melting behavior of b-PE but drastically altered the crystallization behavior depending on the molecular weight and composition of the blend. Adding APP to DEP caused the primary crystallization peak to shift to lower temperature. In the composition range of more than 50 wt % of APP, another new crystallization peak appeared around 70 O C for all blends. This feature was especially pronounced for the blends with the lowest molecular weight APP. Isothermal crystallization studies were carried out for the blends and the data were analyzed by the Avrami theory. The analysis indicates that the dimensionality of the crystallization growth geometry was reduced by blending and each crystallization peak could be correlated with a different dimensionality in the growth geometry. These results are consistent with the framework of the currently accepted microphase separation model for homopolymerldiblock copolymer blends.

Crystallization and Melting Behavior of Nylon 66/Poly(ether imide) Blends

“…Similar conclusion has been confirmed in literature. Sakurai et al 23 and Cohen et al 24 speculate that the structure is kinetically trapped and could not attain a final equilibrium state when the crystallization process is observed by a non-crystallizable component with high Tg. Pizzoli et al concluded that the linear growth rate of spherulite is reduced by 2.5 orders of magnitude as a high Tg component reaches 50% by weight.…”

Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS-graft-PET copolymer on morphology and crystallization behavior

“…This thermodynamic balance is molecular weight dependent, with the critical determinant being the ratio between the molecular weights of the homopolymer (M H ) and copolymer segment (M A ). [12][13][14][15][16] In ternary A/A-block-B/B blends in which Homopolymer A occupies a larger volume fraction, Homopolymer B segregates into microdomains surrounded by A-block-B copolymer. The interfacial area occupied by the block copolymer contains regions in which each copolymer phase is swollen by its respective homopolymer.…”

Morphology and crystallization in mixtures of poly(methyl methacrylate)-poly(pentafluorostyrene)-poly(methyl methacrylate) triblock copolymer and poly(vinylidene fluoride)

“…Most studies have employed homopolymers with repeat units identical to one of the component blocks of the block copolymers. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Only a few studies have considered mixtures where the homopolymer is different from either the block segments of the block copolymer, but is miscible with one of the component blocks. [20][21][22][23][24][25] In an attempt to investigate the effect of the addition of a semicrystalline homopolymer on the phase-separated morphology of a block copolymer in the mixtures, the present study prepares a series of binary mixtures of an fully-amorphous, symmetric triblock copolymer of poly(methyl methacrylate)-b-poly(pentafluorostyrene)-b-poly(methyl methacrylate) (denoted as PMMA-PPFS-PMMA) and a semicrystalline homopolymer of poly(vinylidene fluoride) (PVDF).…”