Tetrafluoroethylene polymers derived from

Several procedures exists for calculating the heats of polymerization for various monomers but they are not very important. It is still more useful to consider the experimentally measured values as the best basis both for theoretical studies and for practical calculations. For ethylene derivatives, the value of — AHlc (from liquid monomer to amorphous solid polymer) ranges from 33.5 kJ mol-1 for a-methylstyrene, through ca. 96 kJ mol-1 for vinyl chloride, to 174 kJ mol-1 for tetrafluoroethylene. 

All tetrafluoroethylene-based homo- and copolymers, described in earlier papers, are semicrystalline with distinct melting points. On the other hand, tetrafluoroethylene-PDD copolymers are totally amorphous and can be tailored for speciflc glass-transition temperatures by altering the polymer composition (1). So these perfluorinated amorphous polymers exhibit properties derived from their amorphous structure and perfluorinated chains. 

The polymers formed from symmetric monomer units, such as polyethylene, (CH2CH2) and polytetrafluoroethylene, (CF2CF2) are an exception to this notation. Although the simplest repeat units are the —CHj— and —CF2— groups, we show two methylene groups and two difluoromethylene groups because they originate from ethylene (CH2= H2) and tetrafluoroethylene (CF2= F2), the monomer units from which these polymers are derived. 

Names for specific polymers which derive from the names of the parent monomers are described as source-based. Most efforts of the lUPAC have been made to develop structure-based names, but source-based names are allowed and the nomenclature for copolymers is source-based. By convention, the name of a homopolymer is the name of the parent monomer, prefixed by poly . If the monomer name consist of more than one word, and for names containing substituents, parentheses are used for example poly(vinyl chloride), poly(tetrafluoroethylene). Also hypothetical monomers can be found in source-based names if the polymer is formed by modification of another polymer (for example poly (vinyl alcohol) which is obtained from modification of poly(vinyl acetate)). Examples for source-based names are given in Table 5.3.1 together with their corresponding structure-based names. Furthermore, common names may be used for monomers which are also used in the corresponding polymer name (see Table 5.3.2). ... 

The separators with pore diameter in the 5-lOnm range are called microporous separators. These separators, in principle, can be organic or inorganic, but the majority of them are derived from organic polymers such as polyethylene, polypropylene, poly(tetrafluoroethylene), and polyfvinyl chloride). Naturally occurring rubber and wood has been used as battery separators. Nonwoven fibers of nylon, cotton, polyesters, and glass can also be employed in the fabrication of microporous separators. 

Low polarisation ratios (<2 1) for absorption had also been found for amorphous PPV (1) deposited from solution by spin-coating on rubbed poly(tetrafluoroethylene) [PTFE]. It is evident that this could be improved on by making use of the high order parameter and self-organising properties of the nematic phase of liquid crystalline electroluminescent polymers such as those (16, 28 and 78-82) shown in Table 6.16. - 2 ° This was then found subsequently to be the case using thermotropic liquid crystalline polyfluorenes, such as 28 and 80 shown in Table 6.6 and segmented PPV derivatives, such as 81. The nematic phase exhibits the lowest viscosity of... 

Billow and Miller [187] also reported fairly similar results for poly(phenylene)s prepared from mixtures of terphenyls. Poly(m-phenylene) [188], phenyl-substituted polyphenylene [189] and perfluoropolyphenylene [190] have thermal and oxidative stabilities similar to that of poly(p-phenylene). Polyphenylenes synthesized by Wurtz-Fittig and Ullmann reactions were reported to withstand heating up to 500°-550°C [187,191,192]. Electrically conductive azo derivatives of polyphenylene (cTo= l-40ohm cm ) were stable up to 300°C without any noticeable decomposition, whereas the conductive block co-polymer of poly-phenylene with p-diethynylbenezene could withstand heating for many hours at 400°-450°C [I], Poly(p-phenylene) as well as poly(tetrafluoroethylene) have been reported to withstand a similar temperature without any thermal degradation and may be used safely up to similar... 

At the other extreme the so-called engineering plastics such as poly(aryl ether ether ketone), poly(tetrafluoroethylene), and poly(2,6-dimethoxy-l,4-phenylene oxide) have high melting temperatures and more extended chain stmctures with correspondingly lower entropies of fusion. Cellulose derivatives are another case in point. As a class of polymers, they are characterized by very high melting points and low heats of fusion. The low entropy of fusion must result from the highly extended nature of the chain. 

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