Synthesis, characterization, and crystallization of syndiotactic alternating ethylene-propylene crystalline copolymer and its blends.

摘要

A syndiotactic alternating ethylene-propylene (SYN-ALT-EP) crystalline copolymer was synthesized by complete hydrogenation, using a diimide reduction, of syndiotactic cis-1,4-poly(pentadiene-1,3) (CIS-PPD). The microstructure was studied by both high resolution nuclear magnetic resonance (NMR) spectroscopy and also fourier transform infra-red (FTIR) spectroscopy. The number average length of syndiotactic sequences is about 69 which indicates a high degree of syndiotacticity (97%) in the microstructure of this copolymer. The single FTIR absorbance at 733 cm{dollar}sp{lcub}-1{rcub}{dollar} without any splitting suggests an alternating arrangement of ethylene and propylene units.; The solution state characterization of SYN-ALT-EP was studied by gel permeation chromatography using on-line measurements of multi-angle laser light scattering (MALLS), single capillary viscosities (VISC), and concentrations by differential refractive index (DRI) detectors. The Mark-Houwink-Sakurada parameters of "K" and "a" in THF at 30{dollar}spcirc{dollar}C are determined to be 8.99 {dollar}times{dollar} 10{dollar}sp{lcub}-5{rcub}{dollar} and 0.8, respectively. The universal GPC calibration curve can be applied to this copolymer in THF at 30{dollar}spcirc{dollar}C.; Two different molecular relaxation processes ({dollar}alpha{dollar} and {dollar}beta{dollar} relaxations) were found via dynamic mechanical (DM) analysis below room temperature: an {dollar}alpha{dollar} relaxation (around {dollar}-{dollar}60{dollar}spcirc{dollar}C) and a {dollar}beta{dollar} relaxation (around {dollar}-{dollar}125{dollar}spcirc{dollar}C). The apparent activation energy of the {dollar}alpha{dollar} relaxation is 285 kJ/mol, and the activation energy of the {dollar}beta{dollar} relaxation is 43 kJ/mol based on the Arrhenius equation. Molecular motion in SYN-ALT-EP copolymer was probed by solid state {dollar}sp{lcub}13{rcub}{dollar}C NMR experiments. At temperatures above T{dollar}sb{lcub}rm g{rcub}{dollar} there are two major molecular motions in this copolymer: a backbone motion (the rotational motion about single bonds) and a methyl side group rotation. The backbone motion is frozen below T{dollar}sb{lcub}rm g{rcub}{dollar}, but the methyl rotation still occurs. As the temperature is further decreased to about {dollar}-{dollar}175{dollar}spcirc{dollar}C, well below the {dollar}beta{dollar}-transition observed in DM analysis, the methyl side group rotation slows down, suggesting that the methyl rotation may be associated with the observed {dollar}beta{dollar} relaxation process.; The equilibrium melting temperature is 55 {dollar}pm{dollar} 1{dollar}spcirc{dollar}C; the equilibrium heat of fusion is 8.8 {dollar}pm{dollar} 0.3 kJ/mol. The overall crystallization kinetics show an Avrami exponent (n) that qualitatively increases with crystallization temperature during primary crystallization. The transition from Regime II to Regime III is observed near T{dollar}sb{lcub}rm c{rcub}{dollar} = 26{dollar}spcirc{dollar}C based on linear crystal growth rate experiments. The fold surface free energy ({dollar}sigmasb{lcub}rm e{rcub}{dollar}) is determined to be 33 erg/cm{dollar}sp2{dollar}.; A monoclinic crystal unit cell was determined (a = 11.19A b = 11.82A c = 9.00A {dollar}gamma{dollar} = 67.03{dollar}spcirc{dollar}) from the fiber pattern via wide angle x-ray diffraction experiments (WAXD). A banded spherulitic morphology was observed by polarized light microscopy (PLM) and transmission electron microscopy (TEM). Such texture is characteristic of the co-twisting of growing lamellae. The morphology changes from regularly banded spherulites to non-regularly banded spherulites and may be correlated with the Regime III to Regime II transition. A plate-like single crystal morphology was also observed by polarized light microscopy after a melt crystallization at small supercooling conditions.; Blends of SYN-ALT-EP/IPP, SYN-ALT-EP/HDPE, and SYN-AL