Oligomers star-shaped

Electropolymerization of star-shaped oligomers 5.18a-c resulted in the formation of highly redox active, cross-linked hyperbranched polymers which led to systems with good conductivities, indicating the presence of multiple pathways for charge carriers provided by the branching units [472],... 

Figure 8.14 Divergent synthesis of star-shaped thioether oligomers by using successive thiol-ene click reaction and esterification reaction. (Reprinted from Tetrahedron Letters, 50, 28, C. Rim, D.Y. Son, Facile and efficient synthesis of star-shaped oligomers from a triazine core, 4161-4163, 2009, with permission from Elsevier.)...

Oligomers of perfluorohexyl-ethene fulfilled these expectations in all preclinical studies, in vitro tests as well in animal tests. A radical polymerisation, followed by ultra-purification steps, created a crystal clear gel-like substance. The behaviours of the mixture of dimeric, trimeric and tetrameric star-shaped species with an inner core of hydrocarbon bonds and an outer layer of perfluoro-alkyl chains could be adjusted by the ratio of the dimeric, trimeric and tetrameric species, using a thin layer distillation. In dependence on this ratio, the viscosity could be adjusted in the range between 90 mPas and 1700 mPas, the specific density between 1.60 g/ml and 1.66 g/ml and the interfacial tension against water between... 

The mechanical properties of the network can also be adjusted by changing the chemical composition of crosslinkable oligomers (Grijpma et al, 2005). For example, D,L-lactide (DLLA) can be ring-opened with TMC in the presence of glycerol to produce star-shaped poly(TMC-co-DLLA) that can then be functionalized with fumarate groups. The incorporation of DLLA increases the Lg of the oligomers and consequently enhances the mechanical properties of the crosslinked network. While the crosslinked fumarate-functionalized network of TMC demonstated a tensile modulus of 1.2 MPa, the network with 86% DLLA had a tensile modulus of 5.3 MPa. 

Shibita, A., Takase, H., Shibata, M., 2014. Semi-interpenetrating polymer networks composed of poly(L-lactide) and diisocyanate-bridged 4-arm star-shaped e-caprolactone oligomers. Polymer 55 (21), 5407-5416. 

Oligomers of DLCs have certain advantages over monomeric DLCs as far as alignment is concerned. Contrary to linear oligomers, star-shaped pentamers and hep-tamers have been found to form macroscopic monodomains of columnar stacks which self-align homeotropically between glass substrates on cooling from the isotropic phase [75]. 

Four-arm star-shaped PDLLA oligomers of controlled molar mass and narrow molar mass distribution were synthesized by using ethoxylated pentaerythritol initiator. The terminal hydroxyl group was converted to methacrylate... 

Growth of the linear oligomer has been monitored by an NMR study of the reaction, involving oxidative addition as the rate-determining step (Scheme 118). The polymer formed is insoluble in solvents. l,2,4,5-Tetra(bromomethyl)-benzene can be used to generate the Pt(iv) complex 960, and this reagent can also be employed to generate star-shaped polymers.Thus, the trinuclear complex 961, prepared from the reaction of 4,4 -di(bro-... 

In contrast to older models of the classical molecular shape of mesogens, some meso-gens are star-like oligomers with flexible central units. 

In polymer synthesis, calixarenes - cyclic phenol-formaldehyde oligomers - are rarely studied and reported. There are two main applications of calixarenes in polymer synthesis use of metal calrxarene complexes as catalysts for polymerization and star-shaped polymers with a calixarene core. 

The organocatalytic transesterification of polylactide using either benzyl alcohol, pentaerythritol or monohydroxyl functional poly(ethylene oxide) oligomers produced either linear (12,13), star-shaped (14, 15) or block polymers (16,17), respectively (Table 2). The reactions were performed in bulk (135 °C) and, at these temperatures, the homogeneous mixtures allowed... 

Star-Shaped Lactic Acid Oligomers for Coating Applications... 

The syntheses of telechelic, star-shaped or hyperbranched oligo- and polyesters reported in this work are based on two "a-b monomers" 3-hydroxy-benzoic acid (3-Hybe) and 3-(4 -hydroxyphenyl)propionic acid (phloretic acid, Phla). These monomers were selected for the following reasons. Polyesters of 3-Hybe melt below 200°C, and they are soluble in various organic solvents (10). Polycondensations of 2-Hydroxybenzoic acid derivatives show a high tendency to yield cyclic oligomers and substituted and imsub-... 

In the previous sections, star-shaped polymers were discussed. In this section, highly branched oligomers or polymers, as distinct from simple star-shaped polymers, will be considered. Several excellent, recent reviews are available on this subject [10-14,47,64,65]. 

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