Polyhydroxyalkanoates (PHAs) have attracted increasing interest as sustainable plastics because of their biorenewability and biodegradability in the ambient environment. However, current semicrystalline PHAs face three long-standing challenges to broad commercial implementation application: lack melt processability, mechanical brittleness, unrealized recyclability, last which is essential for achieving a circular economy. Here we report synthetic PHA platform that addresses origin thermal...

Samples of block copolymers (BCP) constituted by semicrystalline blocks linear low-density polyethylene (LLDPE) and isotactic polypropylene (iPP) different lengths (iPP-b-LLDPE) have been prepared living polymerization using the hafnium-based catalyst that provides high steric control propagation propene units. The LLDPE are random ethylene/1-octene with 1-octene concentrations between 1 3 mol %. crystallization behavior morphologies in melt after iPP-b-LLDPE presented. iPP melts at 135 °C,...

The precise use of a widely available and inexpensive metallocene catalyst enabled the synthesis isotactic polypropylene copolymers characterized by copresence randomly distributed cyclic units in backbone unsaturated pendant employing 1,5-hexadiene as comonomer. Optimization polymerization conditions avoided cross-linking phenomena that negatively affects material processing final properties, resulting good yields samples featuring high molecular masses precisely controlled microstructure....

The memory of crystals in the melt stereodefective samples isotactic polypropylene (iPP), characterized by different concentrations rr stereodefects from 0.49 to 10.5 mol %, was analyzed. Experiments self-nucleation and annealing have demonstrated that high contents stereodefects, largely incorporated iPP, produce a significant persists up temperatures well above melting temperature. For low stereodefect (lower than 2–3 %), is erased at (Ts,DI-DII) only few degrees end endotherm (Tm,end),...

In this review, the phenomenon of polymorphism in polymers is discussed on basis thermodynamic stability different polymorphs that defines conformations chains crystalline lattice and packing mode. particular, we show symmetry energy chain conformation, crystal density entropy packing, presence defects disorder crystals are main factors define mode crystallization induce polymorphism. How specific selected effects molecular structure processing conditions analyzed. particular affects...

Naturally produced, biodegradable polyhydroxyalkanoates (PHAs) promise more sustainable alternatives to nonrenewable/degradable plastics, but biological PHA's stereomicrostructures are strictly confined isotactic (R)-polymers or copolymers of random sequences. Chemical synthesis via catalyzed ring-opening polymerization (ROP) cyclic (di)esters offers expedient access diverse PHA microstructures, including those with defined comonomer sequences and tacticities. However, the alternating PHAs...

Technologically important thermosets face a long-standing end-of-life (EoL) problem of non-reprocessability, more sustainable solution which has resolved to nascent vitrimers that can merge the robust material properties and reprocessability thermoplastics. However, lifecycle is still finite, as they often suffer from significant deterioration mechanical performance following multiple reprocessing cycles, analogous recycling, show undesired creep under working conditions. To address these...

Poly(isoprene)s of different molecular structures have been synthesized with various catalysts based on complexes Nd-, Co-, and Fe-bearing pyridylimine, phosphine, bipyridine ligands. essentially cis-1,4 structure, 3,4 syndiotactic regular alternating cis-1,4-alt-3,4 structure obtained. Moreover, polymers an unusual prevalent but containing units sequences lengths (3 or 5 units) within the chain also The mechanical properties all poly(isoprene)s, some them completely new, investigated. a...

The crystal structures of isotactic and atactic poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) are presented. Samples P3H(Me)2B (at-(R/S)-P3H(Me)2B) the R S enantiomers (it-(R)-P3H(Me)2B it-(S)-P3H(Me)2B, respectively) have been synthesized by ring opening polymerization racemic chiral dimethyl-butyrolactones employing a superbase catalyst. A 1:1 mixture two (it-(R,S)-P3H(Me)2B) has also prepared. Both pure enantiomer polymers crystallize showing identical diffraction patterns, indicating...

The memory of crystalline phase in the melt isotactic polypropylene (iPP) regiodefective samples iPP characterized by different concentrations regiodefects, constituted secondary 2,1 propene units, is studied. self-nucleation (SN) experiments have demonstrated that presence regiodefects produces a strong persists up to temperatures much higher than melting temperature. extension heterogeneous (domain II) containing self-nuclei increases with increasing concentration regiodefects. temperature...

The development of a highly oriented fiber morphology by stretching low stereoregular isotactic polypropylene (iPP) samples is studied at two different temperatures. structural and morphological transformations occurring during deformation are followed in real time collecting situ wide (WAXS) small-angle (SAXS) X-ray scattering data. WAXS analysis reveals that the disordered γ form initially present gradually transforms into mesomorphic iPP room temperature well-oriented crystals α 60 °C....

The crystallization and thermal properties of copolymers isotactic poly(1-butene) (iPB) with ethylene (iPBEt) synthesized a Ziegler–Natta catalyst (E) content between 7 45 mol % are presented. provide evidence multiblock molecular structure these copolymers. samples have been separated in two or three fractions by standard fractionation boiling solvents. Samples concentration lower than 16 surprisingly crystallize form II iPB, polyethylene also occurs for the maximum %. Even more surprising...

Polyethylene-block-syndiotactic polypropylene (PE-block-sPP) crystalline–crystalline block copolymers with different lengths have been synthesized a stereospecific living organometallic catalyst. Samples of PE-block-sPP epitaxially crystallized onto crystals p-terphenyl (3Ph) to achieve control over the crystallization both blocks and study dependence thin film morphology on sequential two by cooling from melt. The epitaxial generates oriented overgrowth sPP PE, highly ordered single...

Isotactic propylene–butene copolymers [i(P-co-B)] with precise and controlled molecular structures were synthesized various organometallic catalysts having different stereoselectivities. Stereoregular stereodefective samples of i(P-co-B) 1-butene (B) content variable in the whole range composition synthesized. All crystallize regardless composition, indicating cocrystallization propene units, which are incorporated unit cells polymorphic forms isotactic poly(propylene) (iPP) poly(1-butene)...

Copolymers of isotactic polypropylene (iPP) with 4-methyl-1-pentene (iPP4MP) were prepared a highly isoselective homogeneous organometallic catalyst in range (4MP) concentrations between about 1.7 and 14 mol %. Crystallization from the melt at different crystallizations temperatures have been performed to study effect 4MP comonomeric units excluded crystals on crystallization α γ forms. All samples crystallize mixtures forms, for each sample, fraction form increases increasing temperature...

β-Myrcene was polymerized with catalysts based on pyridyl-imino complexes of neodymium, iron and copper to highly stereoregular polymers.

Novel 4-methyl-1-pentene/1,5-hexadiene isotactic copolymers (iP4MPHD) incorporating methylene-1,3-cyclopentane (MCP) cyclic co-units with concentrations in the range 4.4–17.6 mol % have been synthesized by using dimethylpyridylamidohafnium/organoboron catalyst. The influence of MCP co-unit on crystallization behavior and mechanical properties poly(4-methyl-1-pentene) (iP4MP) homopolymer has investigated detail. iP4MPHD comonomer content up to 11 crystallize form II iP4MP from polymerization...

Within the large poly(3-hydroxyalkanoate) (PHA) family, C3 propionates are much less studied than C4 butyrates, with exception of α,α-disubstituted propionate PHAs, particularly poly(3-hydroxy-2,2-dimethylpropionate), P3H(Me)2P, due to its high melting temperature (Tm ∼ 230 °C) and crystallinity (∼76%). However, inefficient synthetic routes monomer 2,2-dimethylpropiolactone [(Me)2PL] extreme brittleness P3H(Me)2P largely hinder broad applications. Here, we introduce simple, efficient...

The crystal structures and the polymorphism of polymers are described on basis main principles that define conformation polymer chains in crystalline state modes packing macromolecules. We show presence defects disorder crystals influences polymorphic behavior. cases isotactic poly(butene) (iPB) syndiotactic poly(styrene) (sPS) ilustrated as examples. In case iPB, effect stereoregularity comonomeric units crystallization form I II is an example alteration behavior because modification both...

The mechanical behavior of propylene–pentene isotactic copolymers synthesized with a single-center organometallic catalyst in broad interval pentene (Pe) concentration, from 3 to 50 mol %, is analyzed. All show flexible very high deformation at breaking. presence and entrance Pe counits α δ forms polypropylene (iPP) transform strong fragile iPP homopolymer into ductile materials. stress yield decreases as the content increases, but different has been observed for samples form or form. In...