Frans-poly

In a chain growth polymerization, monomers can be introduced in various ways, most commonly head-to-tail but also head-to-head. In addition, for monomers that remain unsaturated, cis- and fran -configurations have to be considered like for cis- and fran -poly(isoprene). 

Figure 28.3. Structural formulas of several electron-conducting polymers (a) frans-poly(acetylene), (b) cw-poly(acetylene), (c) poly(p-phenylene), (d) polyanUine (PAni), (e) poly(n-methylaniline) (PNMA), (f) polypyrrole (PPy), (g) polythiophene (PTh), (i) poly(3,4-ethylenedioxythiophene) (PEDOT), (j) poly(3-(4-fluorophenyl)thiophene) (PFPT), (k) poly(cyclopenta[2,l-b 3,4-dithiophen-4-one]) (PcDT), and (m) Mg polyporphine.

Figure25 The formation of an all frans-poly(dlm thylsllane) Inclusion comiplex with y-CD.

For the case of polymers which present reversible solid-solid transitions, producing more disordered forms, with increasing the temperature, (e.g. PTFE, ETFE, 1,4-fran.r-poly butadiene (see Sects. 2.5 and 3.2)) the introduction in the chains of comonomeric units, as well as of other constitutional defects, tends to stabilize the more disordered structure with respect to the more ordered one, and hence to lower the transition temperatures. 

An analogous method was used to obtain a new class of macromolecular stereoisomers The hemitactic polymers (99-101). This term refers to a head-to-tail vinyl polymer in which the tertiary carbon atoms constitute two distinct series one, which includes monomer units 1,3,5, 7,..., possesses strict steric regularity, whereas the other, with monomer units 2, 4, 6, 8,. .., is completely at random. In such polymers only one in every two tertiary atoms is influenced by an ordering rule 58 and 59 show the schematic structure of the hemiisotactic and hemisyndiotactic polymers where the white circles indicate the positions of disordered s ubstituents. The hemiisotactic polypropylene was obtained by Farina, Di Silvestro, Sozzani and Savar6 (99, 101) by nonste-reoselective reduction,of. isotactic frans-l,4-poly-2-methylpentadiene. 

Figure 8 Two series of Orthogonal Chromatography runs showing the effec of % n-hept me in the mobile phase of SEC 2 on the fractionation (AA polystyrene, AB poly(styrene co-n-butyl methacrylate) BB poly n-butyl methacrylate). (Reproduced fran Ref. 6. Copyright 1983, American Chemical Society.)...

When palladium ions are bound to poly(ethyleneimine), a soluble polychelatogen, selective conversion of 2-pentyne to ds-2-pentene is achieved under mild conditions (20°C, 1 atm H2, 98% stereoselectivity).170 A dramatic reversal of stereoselectivity (selective formation of frans-2-pentene) is observed, however, if a spacious ligand such as benzonitrile is bound to palladium. 

To 1.07 g of poly(styrene vinylbenzyl chloride) copolymer in EMF was added respectively 51 mg RB for P-RB-51, 102 mg RB for P-RB-102, 152 mg RB for P-RB-152, 305 mg RB for P-RB-305, 450 mg RB for P-RB-450, 610 mg RB for P-RB-610 and 152 mg RB for P-RB-1520. The mixtures were stirred magnetically and heated (80°) for 24 hours. The reaction mixtures were then cooled to ambient temperature. All the polymers were precipitated by addition of an excess of distilled water. They were then purified by precipitating fran DMF solution by excess of methanol and washed continuously with methanol until the final filtrates were colorless. The polymers were dried in a vacuum. 

Nd-boranate-based catalysts were also used in the polymerization of dienes. Nd(BH4)3 (THF)3/TEA yields poly(butadiene) with a frans/cz s-ratio 50/50. If Nd(BH4)3 (THF)3 is combined with a stoichiometric amount of MgBu2 catalyst activities are increased, control of molar masses is improved and poly(diene)s with a trans- 1,4-content of up to 99% are obtained. [348, 349]. 

Cyclohexanedimethylene Terephthalate/PTME Terephthalate Copolymers. Poly ether-ester copolymers based on 1,4-cyclohexanedi-methanol have been prepared using both frans-1,4-cyclohexanedimethanol (f-CD) and a practical grade of 1,4-cyclohexanedimethanol (p-CD) which is reported to contain about a 68/32 mixture of trans- to cis-1,4-cyclohexanedimethanol (26), Gas-phase chromatography of one of our samples of p-CD indicated a 72/28 ratio of trans-to-cis isomer. By use... 

Poly(frans-isoprene), gutta percha (crossl.) 85/250 3000... 

Some information regarding thermal stability of this type of polymer is available in literature. These polymers typically generate CO2, some maleic anhydride, and fragments related to the olefin. For example, poly(maleic anhydride-co-frans-stilbene) (alternating), when heated from ambient to 500° C, generates CO2, styrene, maleic anhydride small amounts of benzene, cyclohexadiene, dimethylbutene, ethylcyclobutanol, and 4-methoxystyrene. Major decomposition products for this polymer are chain fragments (79%), including aromatic, ketonic and unsaturated structures [5],... 

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