Hyperbranched polyesters material properties

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

In the second part of this review, we report the synthesis of dendrimers and hyperbranched polyesters based on 2,2-bis(methylol)-propionic acid. An extensive study has also been made on the material properties of the hyperbranched polyesters both as thermoplastics and as cross-linkable resins. All characterization techniques and apparatus that have been used throughout this work are described in the Appendix. An outline of the material covered is shown in Figure 2. 

The hydroxyfunctional hyperbranched polyesters have been characterized with respect to their mechanical and theological properties, both as thermoplastics and in cross-linked networks. The high number of terminal groups in hyperbranched polymers has a large impact on the properties, and also makes it easy to functionalize the polymers for various applications. One option is to attach reactive groups at chain ends, forming a cross-linkable polymer. Variations in functionality and the type of functional groups will affect both the polymer properties and the final cross-linked material properties. 

Marija Pergal, MSc, works at the Department for Polymeric Materials, Institute for Chemistry, Technology and Metallurgy since 2003 as Research Scientist. Since 2007 she is also Teaching Assistant for the course Chemistry of Macromolecules at Department of Chemistry, University of Belgrade. Her research interests are focused on synthesis and characterization of siloxane homopolymers and copolymers, especially thermoplastic elastomers based on poly(butylene terephthalate) and polyurethanes, as well as polyurethane networks based on hyperbranched polyester. In addition to physico-chemical, mechanical and surface properties of polymers, her particular interest is directed towards the study of biocompatibility of polymer materials. 

In order to compare general properties of hyperbranched polymers and dendrimers, Wooley et al. examined a model hyperbranched polyester and corresponding dendrimer. Pol)miers prepared from 3-hydroxy-5-( eri-butyldi-methylsiloxy)benzoic acid, as branching point, showed that thermal properties, such as Tg and those shown by thermogravimetic analysis (TGA), were independent of pol)mier architecture. However, the dendritic and hyperbranched materials demonstrated comparative solubilities that were much greater than that found for the linear polymer [99]. Their conclusions on the thermal properties may contradict some other findings. For examples, the of hyper-... 

A number of hyperbranched systems have been prepared. These include polyimides with methacryloyl groups at the chain ends, methacrylated polyamine esters, " polyurethane acrylates, polyester acrylates and polyisoph-thalate esters. All materials exhibit 3D sphere like structures with excellent properties. 

Abstract This chapter describes vegetable oil-based polymer nanocomposites. It deals with the importance, comparison with conventional composites, classification, materials and methods, characterisation, properties and applications of vegetable oil-based polymer nanocomposites. The chapter also includes a short review of polymer nanocomposites of polyester, polyurethanes and epoxies based on different vegetable oils and nanomaterials. The chapter shows that the formation of suitable vegetable oil-based polymer nanocomposite can be considered to be a means of enhancing many of the desirable properties of such polymers or of obtaining materials with an intrinsically new set of properties which will extend their utility in a variety of advanced applications. Vegetable oil-based shape memory hyperbranched polyurethane nanocomposites can be sited as an exampie of such advanced products. 

Kou et al., reported using a hyperbranched acrylated aromatic polyester as a modifier in UV eurable epoxyacrylate resin. The material is compatible with the epoxy-acrylate resins. They found that the photopolymerization rate of the resin is promoted by this modifier. Also, the shrinkage of the resin was redueed. At the same time, the tensile, flexmal, compressive strength, and thermal properties of the ultraviolet light eured films are greatly improved. 

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