Structural Studies of Isotactic Poly(tert-butylethylene oxide)

Abstract

bands. The ratios of the 367-to the 412-nm band also agrees reasonably well with the calculated sequence ratios. However, since the bands become closer together as we go to higher wavelengths, overlapping becomes more severe and the intensity measurements, particularly of the 412-nm band, are less precise.The agreement of the observed ratios with the calculated ratios supports the original assignments of the sets to Isotactic Poly(£ert-butylethylene oxide) Studies 205 diads, triads, tetrads, and pentads derived from conjugated diene sequences, and is consistent with a structure arising from 1,4 addition of 1-chloro-l,3-butadiene. These results confirm once again the validity of the theory underlying sequence distribution calculations from copolymerization data. There are few cases which permit such a direct analysis of sequence distribution in copolymerization.

Mechanism of the Stereocomplex Formation between Enantiomeric Poly(lactide)s

“…1 Tadokoro showed that poly(tertbutylene oxide) and poly(tert-butylene sulfide) form racemic lattices, in which R-and S-chains are arranged side by side in 1/1 proportion. 2,3 Firstly, it was reported in 1987 that PLLA and poly(D-lactide) (PDLA) crystallize into a 1/1 stereocomplex which exhibits a 50°C higher melting point than the enantiomeric components. 4 In the last years many investigations were carried out concerning the physical properties of the stereocomplex.…”

Kinetic Analysis on Effect of Poly(4-vinyl phenol) on Complex-Forming Blends of Poly(L-lactide) and Poly(D-lactide)

“…However, by comparison, stereocomlexation is still a rare yet interesting phenomenon in polymers. Several cases have been found by blending tactic polymers of opposite configurations, for examples, isotactic and syndiotactic poly(methyl methacylate)s, 2,3 polythiiranes, 4 polyoxiranes, 5 polylactones. 6,7 The common features of all these systems are that crystallization of enantiomeric polymer chains leads to packing of two different molecular chains into a common crystal lattice, in which the two chains are more densely packed than those of the parent homopolymer crystal lattices.…”

Thermal Properties of Poly(lactic Acid)

“…This was demonstrated by Ikada et al (1987) in a study using X-ray diffraction, which showed the differences of crystalline structure in the formation of a stereocomplex of PDLA and PLLA blending. Tsuji et al (1991) quoted the findings of Sakakihara et al (1973) that when an equimolar ratio of optically active polymers are blended together, the optical compensation of the stereopolymer occurs, leading to inactive materials in the crystalline region or unit cell. The side-by-side packing of stereo complexes can be expected to form a compact, ordered structure with a high melting temperature.…”