Linear flexible aromatic polyester

As flexible substituents, linear and branched alkyl, alkoxy, or thioalkyl side chains of different lengths have been utilized to modify para-linked aromatic polyesters. The main difference to the systems discussed above is the limited thermal stability caused by the substitution with alkyl chains. Also, the mechanical poperties are substantially lowered with increasing... 

CLASS Polyesters linear and flexible aromatic polyesters thermoplastics... 

Synonyms Polyester polyol, aromatic Polyester polyol, crosslinked Polyester polyol, linear Polyester polyol, slightly branched Polyol, flexible Properties Vise. liqs. to waxy solids... 

The aromatic semiflexible polyesters can be formed by varying the dicarboxylic multi phenyl acid structure (naphthalene and diphenol) and non-linear aromatic diol (3,4 -dihydroxybenzophenone). 3,4 -dihydroxybenzophenone can be synthesized from 4-methoxy bromobenzene and m-methoxybenzonitrile via multistep reaction, which can be condensed with respective diacid chloride in o-dichlorobenzene at reflux temperature [43]. It is well known that dimethyl siloxane spacer can make a flexible/semiflexible LC polymer. Thermotropic flexible liquid-crystalline main chain polyesters... 

Unsaturated polyester resins can be formulated to be hard and brittle, tough and resilient, or soft and flexible. By the appropriate choice of intermediates, particularly to form the linear unsaturated resin, special properties can be built into the resin system. As pointed out earlier (Table 12.2), the starting materials used with MA in polyesterifications have different effects upon the extent of isomerization of maleate to fumarate, and this in turn has a strong influence upon the final properties of the cured materials, As shown in Table 12.2, the percentage of fumarate increases considerably as more sterically hindered glycols or aromatic acids are used in the formulations. ... 

Completely rigid rod-like molecules such as poly(4-oxybenzoyl) or poly( p-phenylene terephthalate) tend to be highly crystalline and intractable, with melting points above the decomposition temperature of the polymers (>450°C). The problem of thermotropic MCLCP design is to disrupt the regularity of the intractable para-linked aromatic polymers to the point at which mesomorphic behaviour is manifested below the decomposition temperature and the materials can be processed in fluid yet ordered states. The disruption must not, however, be taken to the stage where conventional isotropic fluid behaviour is preferred. These requirements that the polymer must retain some rod-like nature but at the same time be melt-processable below 400-450°C have limited thermotropic MCLCPs mainly to polymers based on the linear ester or ester/amide bonds. With polyester/ polyesteramides, disruption is normally achieved by the th ee copolymerization techniques outlined in Fig. 8.1, i.e. frustrated chain packing, flexible spacers and non-linear links. 

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