A "grafting from" approach was employed to chemically modify the surface of starch nanocrystals (SNCs) with poly(epsilon-caprolactone) (PCL) chains via Sn(Oct)(2)-catalyzed ring-opening polymerization (ROP) of epsilon-caprolactone (CL). The grafting efficiency was evaluated by suspension tests of resulting SNCs grafted with PCL chains (SNC-g-PCL) carried out in toluene as well as infrared analyses. In a subsequent step, the resulting SNC-g-PCL nanohydrids and neat SNCs were melt-blended in a commercial PCL matrix using extrusion techniques in order to investigate the thermo-mechanical properties of resulting bio(nano)composites. The morphological analyses provided by Atomic Force Microscopy showed that the starch nanoplatelets within the SNC-g-PCL nanohydrids maintained their initial morphology and dimensions even after melt-processing at high temperature. Thermo-mechanical properties were evaluated by differential scanning calorimetry and dynamic mechanical thermo-analysis. They showed a substantial improvement of

Poly(ε-caprolactone)-grafted cellulose nanowhiskers (extracted from ramie: CNWr) synthesized by ring-opening polymerization of the corresponding lactone [1] were studied as “masterbatches” by melt-blending within its commercial poly(ε-caprolactone) matrix (PCL). For sake of comparison, unmodified CNWr were also dispersed in PCL. The goal of this study consists to evidence the impact of the covalent grafting of CNWr surface on thermo-mechanical properties of the commercial matrices. Atomic force microscopy (AFM) attests of the excellent dispersion of the cellulose nanowhiskers within PCL matrix. As a result of the excellent interfacial compatibility between the nanofiller and the matrix, the thermo-mechanical and rheological performances were largely enhanced.

Starting from gypsum as by-product of lactic acid fabrication process, novel high performance composites have been produced by melt-blending PLA and this filler after a previous specific dehydration performed at 500 degrees C for min. 1h. Due to PLA sensitivity towards hydrolysis, the utilization of beta-anhydrite 11 (All) as filler is a prerequisite. Characterized by attractive mechanical and thermal properties due to good filler dispersion throughout the polyester matrix, these composites are interesting in biodegradable rigid packaging or technical applications. interestingly, tensile strength of PLA - All composites proved remarkably high, e.g. higher than 35 MPa at 50 wt-% filler content. However a decrease of impact properties has been recorded. To increase the toughness of these composites while preserving high stiffness an impact modifier based on ethylene copolymer has been mixed with both the polymer matrix and All by melt-compounding. The effectiveness of the impact modifier was confirmed in both neat PLA and All-based composites. Addition Of 510 wt-% impact modifier into highly filled composites (30 to 40 wt-% filler) leads to an attractively threefold increase of impact strength with respect to the compositions without modifier, remarkable thermo-mechanical performances and good filler dispersion.

This article is aimed at revisiting the synthesis of copper-based catalysts immobilized onto crosslinked polystyrene (PS) resins carrying pyridinimine groups (PS-pyridinimine/CuBr). These supported catalytic systems were used for promoting the atom transfer radical polymerization of methyl methacrylate as initiated by ethyl-2-bromoisobutyrate. It was evidenced that the control over the polymerization reaction was strongly influenced by the coordination ability and extent or the transition-metal salt on the supported pyridinimine ligands. For instance, increasing the ligand-to-catalyst molar ratio allowed for increasing the polymerization rate and improving the control over the molecular parameters of the synthesized poly(methyl)methaerylate (PMMA) in terms of the molar masses and molecular weight distributions, The PS-pyridinimine/CuBr supported catalyst was recycled and reused for further polymerization reactions. After two recycling steps, the reaction activity appeared to be preserved, and the control was improved in terms of the initiation efficiency. However, I slight increase in the polydispersity indices was observed. Interestingly, the introduction of a flexible polydimethylsiloxane spacer between the PS support and the catalytic sites led to some more improvement of the control over the molecular parameters of PMMA chains, which displayed narrower molecular weight distributions. (c) 2005 Wiley Periodicals, Inc.

A new supported catalytic system efficient for synthesizing methacrylate-based (co)polymers is described. This catalyst consists of nickel(II) bromide immobilized onto a polystyrene resin carrying triphenylphosphine moieties (PS-PPh3/NiBr2). This system was first used for promoting atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by ethyl 2-bromoisobutyrate ((EBrB)-B-i) in toluene. Used without any additional reagent, this supported catalyst did not promote controlled ATRP of MMA as attested by the low initiation efficiency and the broad polydispersity indices. However, when triphenylphosphine ligand was added, poly(methyl methaerylate) (PMMA) chains of low polydispersity indices were readily recovered, the molecular weight of which linearly increased with monomer conversion and agreed with the expected values. The as-recovered polymers proved to be almost completely deprived of residual transition-metal catalyst. Moreover, the recovered supported transition-metal complex maintained its catalytic activity for additional polymerization reactions without any further addition of fresh catalyst. Only soluble ligand was added in conjunction to monomer, initiator, and solvent to maintain the control over the molecular parameters in terms of molar masses as well as molecular weight distributions.

A new supported catalytic system, i.e. nickel bromide catalyst ligated by triphenylphosphine (TPP) ligands immobilized onto crosslinked polystyrene resins (PS-TPP) is reported. Per se, this catalyst does not allow any control over the polymerization of methyl methacrylate (MMA) initiated by ethyl 2-bromoisobutyrate but, in the presence of a given amount of purposely added free TPP, it promotes controlled ATRP of MMA. Indeed colorless PMMA chains of low polydispersity indices are readily recovered, the molecular weight of which linearly increases with monomer conversion and agrees with the expected values. Recycling of the supported catalyst is evidenced and does not prevent the polymerization from being controlled.

To improve the mechanical properties of granular com starch-filled poly(epsilon -caprolactone) (PCL) compositions, three strategies were investigated including the hydrophobic coating of starch granules by reaction with n-butyl isocyanate, the addition of PCL-grafted dextran (PGD) as an amphiphilic compatibilizer, and the use of PCL-grafted granular starch (PGS). Except for the chemical modification of granular starch by reaction with n-butyl isocyanate, the synthesis of both PGD and PGS relies upon the controlled ring-opening polymerization (ROP) of epsilon -caprolactone (CL) initiated by Al-alkoxides generated onto the polysaccharide, either dextran or starch particles. While the hydrophobic coating of starch only provides higher tensile strength and elongation at break, these properties as well as Young's modulus and strength at yield of the PCL/starch blends were remarkably increased by locating the PCL-grafted dextran at the filler/matrix interface. It is however worth pointing out that a tougher and stiffer material was obtained by melt blending PGS and pure PCL. These property changes were analyzed and clearly related to parameters such as filler dispersion, interfacial tension, interfacial adhesion and reinforcement by PCL crystallites.