Novel Preparation Method for Poly(l-lactide)-Based Block Copolymers:  Extended Chain Crystallites as a Solid-State Macro-Coinitiator

Abstract

A novel synthetic method for poly(L-lactide) (PLLA)-based diblock copolymers was developed by the use of PLLA extended chain crystallites (or crystalline residues) as a solid-state macro-coinitiator. In this study, we showed one example, i.e., a synthesis of diblock copolymer composed of a crystalline PLLA chain and an amorphous poly(DL-lactide) chain by ring-opening polymerization of DL-lactide initiated with stannous octoate (i.e., tin(II) 2-ethylhexanoate) in the presence of PLLA extended chain crystallites. The PLLA extended chain crystallites were prepared by hydrolytic degradation of crystallized PLLA films at 97 degrees C for 70 h. The chains inside the extended chain crystallites are expected to be protected from transesterfication reaction. Gel permeation chromatography, polarimetry, 1H NMR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry revealed that the diblock copolymer poly(L-lactide-block-DL-lactide) was successfully prepared without significant transesterification.

Hydrolytic Degradation

“…Also, Tsuji et al [68] prepared block copolymers by ringopening polymerization of DLLA coinitiated with PLLA crystalline residues (or extended-chain crystallites) prepared by NHD of crystallized PLLA films. Extended-chain crystallites can act as a macrocoinitiator because they have many hydroxyl groups as terminal groups on their surface.…”

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

“…Recently, a novel synthetic method was developed by the use of poly( L ‐lactide) (PLLA) extended chains resulting from the hydrolytic degradation of PLLA crystallized films. Extended chains are anticipated to act as a initiator system with Sn(Oct) 2 because they have many hydroxyl groups 18…”

Polyglycolide as a Biodegradable Nucleating Agent for Poly(L‐lactide)

“…The resolution powers for the FTIR spectra were 2 cm −1 . Gel permeation chromatography and WAXD were carried out by using previously reported procedures 23, 28. WAXD showed that PGA crystallites with orthorhombic unit cells29, 30 are formed at a PGA content of at least above 3 wt.‐% in melt‐quenched PLLA/PGA specimens and that PLLA and PGA crystallize separately to form their respective crystallites.…”