Polylactide (PLA) is a fully biodegradable and recyclable plastic, produced from a bio‐derived monomer: it is a circular economy plastic. Its properties depend upon its stereochemistry and isotactic PLA shows superior thermal‐mechanical performances. Here, a new means to control tacticity by exploiting rotaxane conformational dynamism is described. Dynamic achiral [2]rotaxanes can show high isoselectivity (P
i
=0.8, 298 K) without requiring any chiral additives and enchain by a chain end control mechanism. The organocatalytic dynamic stereoselectivity is likely applicable to other small‐molecule and polymerization catalyses.
Sustainable plastics
sourced without virgin petrochemicals, that
are easily recyclable and with potential for degradation at end of
life, are urgently needed. Here, copolymersand blends meeting these
criteria are efficiently prepared using a single catalyst and existing
commercial monomers
l
-lactide, propylene oxide, and maleic
anhydride. The selective, one-reactor polymerization applies an industry-relevant
tin(II) catalyst. Tapered, miscible block polyesters are formed with
alkene groups which are postfunctionalized to modulate the polymer
glass transition temperature. The polymers are blended at desirable
low weight fractions (2 wt %) with commercial poly(
l
-lactide)
(PLLA), increasing toughness, and elongation at break without compromising
the elastic modulus, tensile strength, or thermal properties. The
selective polymerization catalysis, using commercial monomers and
catalyst, provides a straightforward means to improve bioplastics
performances.
Study of a series of phosphasalen indium alkoxide complexes reveals that the substitution pattern at the phosphorus atoms can deliver outstanding isoselectivity with high rates.
The first report on the use of dinuclear aluminum complexes supported by methylene-bridged phenoxy-imine ligands for the ring-opening polymerization of rac-lactide.
Polylactide (PLA) is af ully biodegradable and recyclable plastic,produced from abio-derived monomer:itis ac ircular economy plastic. Its properties depend upon its stereochemistry and isotactic PLA shows superior thermalmechanical performances.H ere,anew means to control tacticity by exploiting rotaxane conformational dynamism is described. Dynamic achiral [2]rotaxanes can showh igh isoselectivity (P i = 0.8, 298 K) without requiring any chiral additives and enchain by ac hain end control mechanism. The organocatalytic dynamic stereoselectivity is likely applicable to other small-molecule and polymerization catalyses.
Pyridine-containing polymers are promising materials for a variety of applications from the capture of contaminants to the self-assembly of block copolymers. However, the innate Lewis basicity of the pyridine motif...
Pyridine-containing polymers are promising materials for a variety of applications from the capture of contaminants to the self-assembly of block copolymers. However, the coordinative ability and the innate basicity of the pyridine motif drastically limit the scope of pyridine-based monomers that can undergo living polymerization. For example, processes relying on transition metal catalysts are rarely amenable to controlled polymerizations because of coordination of the pyridine nitrogen to the metal center. Herein, we report the expedient synthesis of a family of pyridinonorbornene monomers via a [4+2] cycloaddition between 2,3-pyridynes and cyclopentadiene. Careful structural design of the monomer allowed the preparation of polypyridinonorbornenes via ring-opening metathesis polymerization (ROMP) with living characteristics. These unusual macromolecules exhibited high Tg and Td. Investigation of the polymerization kinetics and of the reactivity of the chain ends shed light on the influence of monomer coordination on the chain-growth mechanism.
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