Liquid crystalline hyperbranched polymer

Scheme 6.9. Ringsdorf et al. s[434 preparation of hyperbranched liquid crystalline polymers possessing chiral capping units.

Scheme 7.6. Preparation of a hyperbranched liquid crystalline polymer possessing mesogenic building blocks and chiral termini.

Keywords Liquid crystalline polyester, liquid crystalline polymer blend, liquid crystalline polymer composite, hyperbranched liquid crystalline polymer, mechanical stability, thermal stability, reactive liquid crystalline polymer... 

Macromolecules dendritic, 285 hyperbranched, 284-286 Main-chain liquid crystalline polymers, 49 Main-chain polyester LCP mesogenic units, 50... 

Side-chain liquid-crystalline polymers with controlled molecular weights have been obtained by the polymerization of FM-25 with 1-22 (X = Br)/CuBr/ L-3 in the bulk at 100 °C, to examine the thermotropic transition as a function of the MWD.324 Second-order nonlinear optical materials with branched structure were prepared by the copper-catalyzed radical polymerization of FM-26 and FM-27 using hyperbranched poly[4-(chloromethyl)styrene] as a multifunctional initiator.325... 

Dendritic polymers are most often reported to be amorphous, which can be anticipated from their highly branched architecture. However, some exceptions are presented in the literature. Percec et al. [34,35] reported on liquid crystalline (LC) hyperbranched polymers where the LC-phase was achieved by conformational isomerism. Various repeat units of A2B type have been used where a flex-... 

Kim reported on liquid crystalline properties observed for hyperbranched aromatic amides obtained from 3,5-diaminobenzoic acid and derivatives thereof. The resulting polymers exhibited nematic liquid crystalline phases [89]. 

Branching in polymers generally reduces the crystallization tendency for conventional polymers. Therefore, hyperbranched polymers were first believed to behave as amorphous polymers due to the highly branched backbone. Several papers have, however, shown that both liquid crystalline and crystalline hyperbranched polymers can be made from some special A B monomers or by attachment of crystallizable end groups. 

Percec et al. have described the possibility of making hyperbranched polymers which exhibit liquid crystalline phases [34, 35]. They made hyperbranched polyethers based on an A B monomer having both a spacer and a... 

Hyperbranched polymers are often referred to as amorphous polymers since the branching of the backbone reduces the ability to crystallize in the same manner as linear polymers. Some exceptions have, however, been presented where the polymers have been modified to induce liquid crystallinity [34,35] or crystallinity [36] (Sect. 3.6.1). 

Ujiie S, Osaka M, Yano Y et al (2000) Ionic liquid crystalline systems with branched or hyperbranched polymers. Kobunshi Ronbimshu 57 797-802... 

Marcos M, Alcala R, Barbera J et al (2008) Photosensitive ionic nematic liquid crystalline complexes based on dendrimers and hyperbranched polymers and a cyanoazobenzene carboxylic acid. Chem Mater 20 5209-5217... 

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... 

Nguyoi HH, Valverde Serrano C, Lavedan P, Goudouneche D, Mingotaud AF, Lauth-de Viguerie N, Marty JD (2014) Mesomorphic ionic hyperbranched polymers effect of structural parameters on liquid-crystalline properties and on the formation of gold nanohybrids. Nanoscale 6 3599 3610... 

The liquid crystalline unit-containing polymers begin a timid entry in the TPE field. The liquid crystalline sequences can be part of the backbone or may be present as side chains. Nair et al. [200,201] carried out an abundant and very valuable work with both fundamental and applied aspects. These polymers are prepared by chain polymerization or by polycondensation and are discussed in Chapter 2. Some of them are blends and the morphology and properties of Rodrun LC3000 were the subject of two articles [202,203]. The first applications and patented products are very promising and their development should enjoy a rapid increase. This holds also for the introduction of hyperbranched and dendritic segments in block copolymers [204]. 

Due to dieir compact, branched structure and to die resulting lack of chain entanglement, dendritic polymers exhibit much lower melt and solution viscosity dian their lineal" counterparts. Low a-values in die Mark-Houwink-Sakurada intrinsic viscosity-molar mass equation have been reported for hyperbranched polyesters.198 199 Dendrimers do not obey diis equation, a maximum being observed in die corresponding log-log viscosity-molar mass curves.200 The lack of chain entanglements, which are responsible for most of the polymer mechanical properties, also explains why hyperbranched polymers cannot be used as diermoplastics for structural applications. Aldiough some crystalline or liquid... 

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