Macromolecular design of specialty polylactides by means of controlled copolymerization and stereocomplexation

Abstract

Among the bio-based polymers thus developed, poly-L-lactide (PLLA) has been the most widely used in many fields because of its excellent cost-property balance.However, the properties and functionalities of PLLA cannot easily be controlled as the conventional petroleum-based polymers, retarding the progress of its manufacturing in large scale. One approach to obtain high-performance and specialty polylactides is to use stereocomplex-type polylactides (sc-PLA) that can be obtained by mixing PLLA and its enantiomer poly-D-lactide (PDLA). The other approach is to use copolymers consisting of polylactides (PLA) and other types of macromolecular chains. Here we demonstrate how such high-performance and specialty PLA polymers can be designed and synthesized. These macromolecular designs and synthetic methodologies are This article is protected by copyright. All rights reserved.This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/pi.5172 Accepted Articlehighly effective for controlling the structure and properties of the PLA polymers for use as biomedical and high-end industrial materials.Key words: polylactides, stereoblock, polymer blend, copolymerization, surface immobilization 1) IntroductionPolymeric materials prepared from renewable natural resources are now being accepted as ''bio-based polymers''. These polymers are characterized by the new processing method called ''white biotechnology'' where bio-engineering using fermentation and plant biotechnology is focused as the principal technology. It is evident that the bio-synthesis of a number of key monomers (so-called platform chemicals) such as succinic and 2,5-furandicarboxylic acids has been progressing quite rapidly. Even terephthalic and adipic acids may possibly be replaced by the ones synthesized from these bio-based monomers and chemicals. This article is protected by copyright. All rights reserved. Accepted ArticleOther biomass-originated polyamides such as Nylon 11, polyesters such as poly(ethylene furanoate) (PEF), and isosorbide-based polycarbonate (Is-PC) will also be manufactured in large scale very soon. Some of these biobased polymers were once developed as biodegradable polymers that can be broken down into environmentally friendly substances by composting. However, their application was limited to temporal use at low cost, and their market has not become large enough. For replacing structural materials made of oil-based polymers, high-performance bio-based polymers ought to be developed because toughness and durability are needed for these applications.Among the bio-based polymers mentioned above, PLLA has taken a special position because of its balanced properties and cost performance. It can readily be prepared by ring-opening polymerization (ROP) of L-lactide monomer synthesized from L-lactic acid, a fe...

Indium Catalysts for Ring Opening Polymerization: Exploring the Importance of Catalyst Aggregation

“…Stereocontrol in metal-mediated ROP of LA can arise through two mechanisms: (1) enantiomorphic site control and (2) chain-end control. − These two mechanisms are not necessarily independent and may both play an important role at different points in the polymerization process . Controlling the physical properties of PLA through metal catalysis, for example, through the stereoselective polymerization of rac -LA ,,,− or the copolymerization of LA and other cyclic esters ,,− has become an important avenue toward the widespread replacement of traditional nondegradable plastics with biodegradable options ( vide infra ).…”

Self-Assembly of Triblock Copolymers from Cyclic Esters as a Tool for Tuning Their Particle Morphology

“…In addition to the ability for supramolecular chain extension achieved by capping UPy chains, we took additional advantage of dually associated stereocomplexes, − thereby combining hydrogen-bonding interactions of enantiomeric PLLAs and PDLAs with the association of UPy end groups between macromolecules. Moreover, by the alteration of comonomers repeating units in copolymers, we tuned the rigidity of the macromolecules.…”

“…Microparticles and nanoparticles of stereocomplexes composed of polylactide (PLA) and its copolymers with other aliphatic polyesters receive much attention, because of their potential use in biomedical and pharmaceutical applications. − The synthetic route, most widely used for the preparation of biodegradable and biocompatible copolyesters, is based on the sequential ring-opening polymerization (ROP). However, this method of synthesis requires appropriate conditions for the elimination of even traces of impurities, and suppression of segmental exchange by transesterification .…”

Synthesis and mechanochemical properties of biobased ABCBA‐type pentablock copolymers comprising poly‐d‐lactide (A), poly‐l‐lactide (B) and poly(1,2‐propylene succinate) (C)

“…However, when PLLA and PDLA having molecular weights higher than 100 kDa are mixed, homo‐chiral (hc) crystals of respective polymers are likely formed in preference to the stereocomplex (sc) crystals. In our previous study, we demonstrated that stereoblock‐type polylactides (sb‐PLA) combining both PLLA and PDLA sequences in one macromolecular chain exhibited a highly improved stereo complexibility even when they have high molecular weights 6–11 . By the neighboring arrangement of the enantiomeric block sequences, the sc formation can be much easier in the sb‐PLA.…”