Siloxane hyperbranched

Scheme 6.14. Synthesis of siloxane hyperbranched polymers effected by Pt-catalysis.

In 1999, Muzafarov and coworkers published a preliminary report describing the synthesis of a hyperbranched poly(siloxane) from triethoxysilanol via a rapid, ammonia-catalyzed condensation process (Scheme 28)192. The authors acknowledged the potential difficulties of this process (e.g. head-head condensation leading to crosslinked products) but presented 29Si NMR data to support their conclusion that hyperbranched polymer was formed. The fact that no gel formation was observed also suggested that the polymerization proceeded as expected. The polymer, a transparent, yellow liquid, was characterized with NMR and IR spectroscopy, and GPC. 

Quenching with the aminated resin appeared absolutely necessary to avoid cleavage of the aminopropylpolysiloxane. After filtration, the aminopropyl-polysiloxane can be stored at -18°C in the CH Cl /MeOH solution without decomposition. Analysis by SEC can be made from THE solutions prepared after incomplete evaporation of the CH Clj/methanol mixture. Actually, they cannot be easily stored for long times and the polymers cannot be dried without degradation. Their sensitivity to TMSI appeared much higher compared with NBoc-functionalized hyperbranched poly(siloxysilanes) or NBoc-functionalized highly crosslinked siloxanes networks formed by sol-gel chemistry [27]. 

Figure 5.23. The general strategy (a) and examples (It-c) of hyperbranched polymer network structures featuring a siloxane crosslinkage. Reproduced with permission from Meijer, D. Dvornic, R R. Fall 2005 ACS meeting, Midland, Ml.

Figure 3. Rebrov s seminal synthesis of hyperbranched poly(siloxanes)...

The units giving rise to the liquid-crystalline behavior can be in the side chains. Although most of the polymers studied have been linear, there has been some work on hyperbranched or comb-like structures. The orientation of the mesogenic groups is important. " Frequently backbones include siloxanes and acrylates, " but a variety of other structures... 

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. 

The synthesis and properties of star polymers and dendrimers functionalized with ferrocene units has attracted a great deal of attention. The synthesis of high-generation dendrimers functionalized with chiral ferrocenyl units in their structures has been reported. The chiroptical properties of this class of dendrimer was dependent on the number of ferrocenyl groups and their chemical environment, but not on their position within the dendrimer. Deschenaux has reported the synthesis of hquid crystalline ferrocene-based polymers prossessing an enantiotropic smectic A phase. Ferrocene-functionahzed cyclic siloxane (29) and silsesquioxane branched polymers have also been reported. A hyperbranched polymer with a cubic silsesquioxane core was used to mediate the electrocatalytic oxidation of ascorbic acid. 

Linear, graft, hyperbranched, and star copolymeric siloxanes obtained via anionic ring-opening copolymerization of functional cyclotrisiloxanes were used as supports for transition metal catalysts. ... 

A large number of different monomers such as cyclic ethers, acetals, amides, esters, and siloxanes are used in ring-opening polymerizations (ROPs) to obtain linear polymers for a variety of everyday applications. Nevertheless, ring-opening strategies have also heen established as a versatile method for the s)mth-esis of hyperbranched homopolymers as well as other complex macromolecular architectures in the recent years. 

Size exclusion chromatography-mass spectroscopy has been applied to structural and molecular weight studies on silicon containing polymers including hyperbranched alkoxysiloxane [30], polydimethyl siloxane [31], methyl acryloxypropyl trimethoxy silone [32] and phosphazines. 

The proposed chapter reviews the work done on 6FDA based fluorinated Pis with respect to its synthesis and various copolymers, polymerisation methods, poly(ether-imide), photosensitive polyimide, hyperbranched polyimide, addition polyimide, poly(amide-imide), poly(urethane-imide), poly(epoxy-imide), poly(ester-imide), poly(siloxane-imide), nanocomposites and non-linear optical polyimides. Finally, its application in electronics and use as a material for gas separation and corrosion protection are discussed. 

Concerted efforts to examine the synthesis and polymerization of such ABx monomers was however not attempted until 1989 when Kim and Webster (17) reported their preparation of hyperbranched polyphenylenes fi-om the AB2 monomers, 3,5-dibromophenyl boronic acid, 7, or 3,5-dibromophenyl magnesium bromide, 8 (Figure 1). In a similar way to dendrimers, the field of hyperbranched macromolecules has been extended considerably since this initial report. Hyperbranched polyesters based on fully aromatic, fiilly aliphatic, or partially aliphatic/aromatic systems have been extensively studied by a number of groups (18-20). Similarly, hyperbranched poly(etherketones) (21), poly(ethers) (22), poly(urethanes) (23), poly(siloxanes) (24), etc. have been prepared using classical step growth chemistry. 

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