Structure and Properties of Metallosupramolecular Polymers with a Nitrogen-Based Bidentate Ligand.

The solid-state properties of supramolecular polymers that feature metal-ligand (ML) complexes are, in addition to the general nature of the monomer, significantly affected by the choice of ligand and metal salt. Indeed, the variation of these components can be used to alter the structural, thermal, mechanical, and viscoelastic properties over a wide ranges. Moreover, the dynamic nature of certain ML complexes can render the resulting metallosupramolecular polymers (MSPs) stimuli-responsive, enabling functions such as healing, reversible adhesion, and mechanotransduction.

Plasticization of a Semicrystalline Metallosupramolecular Polymer Network.

The assembly of ligand-functionalized (macro)monomers with suitable metal ions affords metallosupramolecular polymers (MSPs). On account of the reversible and dynamic nature of the metal-ligand complexes, these materials can be temporarily (dis-)assembled upon exposure to a suitable stimulus, and this effect can be exploited to heal damaged samples, to facilitate processing and recycling, or to enable reversible adhesion. We here report on the plasticization of a semicrystalline, stimuli-responsive MSP network that was assembled by combining a low-molecular-weight building block carrying three 2,6-bis(1'-methylbenzimidazolyl) pyridine (Mebip) ligands and zinc bis(trifluoromethylsulfonyl)imide (Zn(NTf)).

Mechanical Behavior of Thermoplastic Starch: Rationale for the Temperature-Relative Humidity Equivalence.

This paper aimed at understanding and rationalizing the influence of both temperature and relative humidity on the mechanical behavior of thermoplastic starch (TPS). DMA experiments revealed that water molecules impact the crosslinking network by reducing the intermolecular hydrogen bond density, resulting in a less dense entanglement network. In addition, the in-situ X-ray characterization during hydration of starch revealed structural changes, which were ascribed to conformational changes in the starch chain, due to their interaction with the uptake water molecules.

Lactide Lactone Chain Shuttling Copolymerization Mediated by an Aminobisphenolate Supported Aluminum Complex and Al(OPr): Access to New Polylactide Based Block Copolymers.

The chain shuttling ring-opening copolymerization of l-lactide with ε-caprolactone has been achieved using two aluminum catalysts presenting different selectivities and benzyl alcohol as chain transfer agent. A newly synthesized aminobisphenolate supported aluminum complex affords the synthesis of lactone rich poly(l-lactide--lactone) statistical copolymeric blocks, while Al(OPr) produces semicrystalline poly(l-lactide) rich blocks. Transalkoxylation is shown to operate efficiently.

A one pot one step combined radical and ring-opening route for the dual functionalization of starch in aqueous medium.

Starch based materials are attractive bio-based alternative to fully synthetic polymers. Native starch has however limited thermoprocessability and properties and must be modified. In order to improve the properties of starch-graft-poly(butyl-acrylate-co-styrene) copolymers via a process as green as possible, we report herein a new method for the dual functionalization of the polysaccharide via a one pot one step reaction in aqueous medium combining free radical polymerizations and ring-opening chemistry.

Organocatalytic sequential ring-opening polymerization of a cyclic ester and anionic polymerization of a vinyl monomer.

Organocatalysis has provided new tools for making block copolymers, in particular active species able to polymerize monomers of different chemical nature such as cyclic esters, cyclic carbonates and epoxides. We report herein the first example of an organocatalytic active species able to polymerize sequentially a cyclic ester, ε-decalactone, and a vinyl monomer, methyl methacrylate. The resulting block copolymer shows the properties of thermoplastic elastomers.

Impact of Nanoconfinement on Polylactide Crystallization and Gas Barrier Properties.

The barrier properties of poly(l-lactide) (PLLA) were investigated in multinanolayer systems, probing the effect of confinement, the compatibility between the confining and the confined polymer, crystal orientation, and amorphous phase properties. The multilayer coextrusion process was used to confine PLLA between two amorphous polymers (polystyrene, PS; and polycarbonate, PC), which have different chemical affinities with PLLA. Confined PLLA layers of approximately 20 nm thickness were obtained.

Uranyl Cation Incorporation in the [PWO] Macrocycle Phosphopolytungstate.

Association of uranyl nitrate with the macrocycle [PWO] in formate buffered aqueous solution leads to the formation of a new compound (KLiNa)[(UO)(HCOO)(PWO)Cl]·89HO (1). Its characterization by XRD reveals a high disorder of the uranyl cations and the formation of monodimensional chains of anionic [(UO)(HCOO)(PWO)Cl] entities linked through formate ligands. The uranyl species are located either in the coordinating sites of the macrocycle [PWO] or at its surface.

Formation of a new type of uranium(iv) poly-oxo cluster {U} based on a controlled release of water esterification reaction.

A new strategy for the synthesis of large poly-oxo clusters bearing 38 tetravalent uranium atoms {U} has been developed by controlling the water release from the esterification reaction between a carboxylic acid and an alcohol. The molecular entity [UOCl(HO)(ipa)]·(ipa) (ipa = isopropanol) was crystallized from the solvothermal reaction of a mixture of UCl and benzoic acid in isopropanol at temperature ranging from 70 to 130 °C. Its crystal structure reveals the molecular assembly of the UO fluorite-like inner core {U} with oxo groups bridging the uranium centers.

Processing of PVDF-based electroactive/ferroelectric films: importance of PMMA and cooling rate from the melt state on the crystallization of PVDF beta-crystals.

Poly(vinylidene difluoride) (PVDF) displays attractive ferroelectric/piezoelectric properties and its polar β-crystals are specifically targeted for achieving electroactive applications. However, their direct crystallization from the melt state represents a challenging task that has never been addressed using melt-state processes. The use of poly(methyl methacrylate) (PMMA) is herein investigated to promote the PVDF polar β-phase using melt-blending and extrusion-calendering technologies.

Influence of fatty chain length and starch composition on structure and properties of fully substituted fatty acid starch esters.

A series of almost fully substituted Fatty Acid Starch Esters (FASEs) has been obtained in a homogeneous LiCl/DMAc medium by grafting octanoyl (C8), lauroyl (C12) and palmitoyl (C16) chlorides onto 3 starch species: Amylo-Maize, Potato and Waxy Maize. Structure-property relationships of FASEs are investigated as a function of both fatty acid chain length and amylose/amylopectin ratio of the starch. The structural study has revealed a layered type organization in which starch chain planes are separated by fatty chains.

Optimum pressure for the high-pressure polymerization of urethane dimethacrylate.

Objectives: The aim of this study, part of our research to improve properties of resin composite blocks suitable for CAD/CAM and to better understand underlying mechanisms associated with high-temperature/high-pressure (HT/HP) polymerization, was to determine an optimum polymerization pressure of urethane dimethacrylate (UDMA) in the presence of an initiator (0.5% benzoyl peroxide) by determining the degree of conversion (DC) and viscoelastic properties of polymers obtained at 90°C under varying HP.

Methods: DC and viscoelastic properties of 16 UDMA polymers, two controls (thermo-cured and thermo-cured followed by post-cure relaxation) and 14 experimental groups (HP polymers, in the range of 50-350 MPa, in 50 MPa increments, without and with post-cure relaxation) were determined via near infrared spectroscopic analysis and dynamic mechanical analysis, respectively.

Dynamic mechanical analysis of high pressure polymerized urethane dimethacrylate.

Objectives: The aim of this study was to compare the viscoelastic properties of high pressure (HP) polymerized urethane dimethacrylate (UDMA) with those of control, ambient pressure thermo-polymerized and photo-polymerized, UDMA and to assess the effect of varying polymerization parameters (protocol, temperature, and initiator) on the viscoelastic properties of HP polymerized UDMA.

Methods: The viscoelastic properties of the two control polymers, polymerized under atmospheric pressure, and four experimental polymers, polymerized under HP, were determined via dynamic mechanical analysis (DMA), in three point bending configuration. Atomic force microscopy (AFM) was used to characterize fractured polymer surface morphologies.

Isoprene-styrene chain shuttling copolymerization mediated by a lanthanide half-sandwich complex and a lanthanidocene: straightforward access to a new type of thermoplastic elastomers.

A lanthanide half-sandwich complex and a ansa lanthanidocene have been assessed for isoprene-styrene chain shuttling copolymerization with n-butylethylmagnesium (BEM). In the presence of 1 equiv BEM, a fully amorphous multiblock microstructure of soft and hard segments is achieved. The microstructure consists of poly(isoprene-co-styrene) blocks, with hard blocks rich in styrene and soft blocks rich in isoprene.

Water barrier properties in biaxially drawn poly(lactic acid) films.

Crystallization is among the easiest ways to improve polymer barrier properties because of the tortuosity increase within the material and the strong coupling between amorphous and crystalline phases. In this work, poly(lactic acid) (PLA) films have undergone α' thermal crystallization or different drawing processes. Although no effect of α' thermal crystallization on water permeability is observed, the drawing processes lead to an enhancement of the PLA barrier properties.