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The knowledge of the photodegradation mechanisms and the possibility to modify them is a very important topic, especially for the novel biopolymers, as their durability with respect to the petro-plastics is yet an open question. Among the biopolymers, aliphatic polyesters are an emerging class of materials, thanks to the possibility of preparing them from renewable resources and their potential environmental degradability. In this study two aliphatic molecular structures, containing 1,4-cyclohexylene units, have been used: poly(butylene 1,4-cyclohexanedicarboxylate) (PBCHD) and poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCCD). Moreover, in order to increase the durability, titanium dioxide (TiO 2 ), known for its capability of absorbing UV radiation, was incorporated into the polymer. Therefore, composites containing different amount of titania, in the anatase and rutile crystalline phases separately, have been prepared by using a Brabender mixer. Both matrixes and composites were exposed to UV irradiation in an accelerated photo-ageing device and the modifications in their chemical structures were analysed by UV and IR spectroscopies. It results that the photodegradability of PBCHD, containing only one cycle per repeating unit, is lower than that of PCCD and that the composites have a photodegradability lower than those of the homopolymers. The well dispersion of the particles and the good adhesion between TiO 2 and polymer have been checked by SEM observations. The protection of TiO 2 against the photooxidation increases with the particle content and results higher for the anatase crystalline phase. [ABSTRACT FROM AUTHOR]

The aliphatic counterparts of the most used aromatic polyesters (PET, PPT, and PBT) have been synthesized by a two-stage polycondensation process, starting from dimethyl 1,4-cyclohexane dicarboxylate and different diols. The fully aliphatic polyesters are characterized by two cis/trans isomeric ratios (50 and 90 mol%) of the 1,4-cycloaliphatic rings. According to the cis/trans content, the properties of the materials notably change. Indeed, polymers rich in trans isomer are semicrystalline, whereas polymers with low trans content are fully amorphous, due to the presence of kinks along the chain. Trans isomer is characterized by higher rigidity than the cis one and the corresponding polymers have high glass transition temperatures. Moreover, the length of the methylene sequences in the diol has a notable influence on the final thermal and mechanical properties. Therefore, tunable properties can be easily obtained. This characteristic, in association with good mechanical performances, potential sustainability of the monomers and biodegradability, makes these aliphatic polyesters an interesting class of polyesters for some specific applications. [ABSTRACT FROM AUTHOR]

In the field of aliphatic polyesters there is a great interest in building novel macromolecular structures that may effectively feature the required properties for specific applications. For this reason, it is extremely important to understand the correlations between chemical structure and final performance. Monomers based on the 1,4-cyclohexylene unit are interesting as they are potentially bio-based and rigid enough to improve glass transition and melting temperatures. The present paper describes the preparation of samples of poly(1,4-cyclohexylenedimethylene adipate), characterized by different cis/trans isomeric ratio of the cyclic units, the analysis of their thermal properties and the comparison with the properties of similar polymers such as poly(butylene adipate), poly(butylene-1,4-cyclohexanedicarboxylate) and poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate). The effect of the rigidity and of the stereochemistry of the 1,4-cyclohexylene unit on the thermal properties was analysed. Such an effect reaches its maximum level when the cyclic-containing monomers are the diacid or the diester and when the trans isomers predominate. Starting from such a result, the combination of specific cyclic building blocks with the correct cis/trans ratio makes it possible to build macromolecular structures with the required final properties. [ABSTRACT FROM AUTHOR]

The synthesis of novel poly(butylene dodecanoate)s containing different percentages of glycerol was successfully carried out. The polyesters are characterized by branched or cross-linked molecular structures, according to the glycerol content. The modification of the linear backbone of the poly(butylene dodecanoate) increases the rigidity and induces significant changes in the polymer behavior toward photodegradation with respect to UV irradiation. Such a result could be very significant for specific outdoor applications of the novel polyesters. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of the randomness degree and block length of polyamides after interchange reactions is a key issue to estimate the transamidation progress, which strongly influences the final properties of the materials. The polymers under examination are poly(m-xylylene adipamide) (MXD6) and poly(hexamethylene isophthalamide-co-terephthalamide) (PA6I-6T). They were blended by extrusion and then treated in differential scanning calorimeter (DSC) in order to improve transamidations and copolymer formation. The molecular structure of the final materials was analysed by means of an efficient, new and fast method based on 1H NMR analysis. The results were compared to those obtained by the more widely used 13C NMR analysis. [Copyright &y& Elsevier]

Abstract: Poly(butylene terephthalate) ionomers with imidazolium groups selectively located as end-groups (telechelic) have been prepared by melt polycondensation adding a hydroxyl derivatized imidazolium salt at the beginning of the polymerization process. The design of the chemical structure of the imidazolium salt is of fundamental importance in order to achieve the synthesis of ionomers with good thermo-mechanical properties. The final ionomers present high molecular weight, good color, transparency and thermal stability. Imidazolium ionomers present good antimicrobial (AM) properties comparable with those of commercial AM agents. The incorporation of the ionic groups in the polymer chain prevents their migration during use and therefore the antimicrobial activity can be preserved for longer time. [Copyright &y& Elsevier]

Abstract: Bisphenol A polycarbonate telechelic sulfonated ionomers have been prepared by melt polycondensation using bis(methyl salicyl) carbonate (BMSC), bisphenol A (BPA) and the sodium salt of sulfobenzoic acid phenylester (SBENa). Using an activated carbonate such as BMSC it is possible to decrease both reaction temperature and time respect to a standard polycondensation that use diphenylcarbonate (DPC) as carbonate precursor. Using the activated carbonate, ionomers with low Fries by-products and with good color have been obtained. The addition of SBENa permits the preparation of telechelic ionomers with ionic contents up to 3mol%. All the properties of the telechelic ionomer obtained using BMSC are superior respect to those of the telechelic ionomers obtained using DPC. In particular, the ionomers prepared using BMSC are stable up to 400°C and present higher glass transition temperature and storage modulus respect to standard PC. [Copyright &y& Elsevier]