Cycloaddition polymerization

A cation radical chain cycloaddition-polymerization catalysed by tris(4-bromophenyl)aminium hexachloroantimonate has been reported to afford polymers with an average molecular weight up to 150000. Both cyclobutanation and Diels-Alder polymers were obtained. " The reactivity of the phospine radical cation towards nucleophiles was studied. Tributylphosphine reacted with l,l-dimethyl-4,4-bipyridinium (methyl viologen, MV) in the presence of an alcohol or thiol (RXH X = O, S), which resulted in the gradual formation of the one-electron reduced form... 

A series of -conjugated poly(dithiafulvene)s (12) have been prepared by cycloaddition polymerization of aldothioketenes and their alkynethiol tautomers, which were derived from aromatic diynes (Scheme 3) [70-73]. Efficient expansions of -conjugation systems in the polymers were evident... 

We have reported the first electroactivity of a thioketene dimer compound [116]. The CV measurement of 2,4-dibenzylidene-l,3-dithietane (31), which was prepared by a basic dimerization of phenylthioketene derived from ben-zyltriphenylphosphonium chloride, showed irreversible two-step oxidation peaks at 0.25 and 0.61 V vs Ag/Ag+, indicating that 31 acts as a stronger electron donor than 2,6-bisphenyl-l,4-dithiafulvene (30) and TTF (2). The dimer (31) can form a 1 1 CT complex with TCNQ in DMSO. Cycloaddition polymerization of bisthioketene derived from p-xylenebis(triphenylphosphoni-um chloride) gave a -conjugated polymer (32) with thioketene dimer unit in the main chain (Scheme 12). This polymer was the first polymer contain-... 

Scheme 44. Cation radical chain cycloaddition polymerization.

The homopol5unerization of diisocyanates is only useful for specialty diisocyanates, such as aliphatic 1,2- or 1,3-diisocyanates (3) and aromatic o-diisocyanates (4), which polymerize via cycloaddition processes. Anionic homopolymerization of monoisocyanates takes place by addition across the 0=N bond to form nylon-1 polymers. Polyamides are also obtained fi"om diisocyanates and enamines or ketenaminals. This reaction proceeds by a [2 -i- 2] cycloaddition reaction with subsequent ring opening to form polyamides. [2 - - 4] cycloaddition polymerization to form heterocyclic polymers is observed with carbonyl diisocyanate (5). Ring-opening polymerization occurs in the reaction of bis-epoxides... 

Glycidyl ethers derived from bisphenol A (15) or diglycidyl tetrephthalate can also be used as monomers in diisocyanate reactions. The reaction of 2,4-TDI with 15 proceeds by ring-opening [2-1-3] cycloaddition polymerization across the 1,3-dipol generated from the bis-epoxides to form a linear poly(2-oxazohdinone) (16) (76). 

A tris(4-bromophenyl)ammonium hexachloroantimonate catalyst has been utilized to promote a cation radical mechanism in the Diels-Alder cycloaddition polymerization of a bis(diene) with an ionizable bis(dienophile) (Scheme 2). The polymers were obtained with molecular weights up to ca 10 000 and a polydispersity index of ca 2. The electron-transfer reactions of phenols and its derivatives are also important to the polymer industry for the stabilization of polymers, fats and oils. Pulse radiolysis of naphthols and hydroxybiphenyls in n-butyl chloride at room temperature forms two species-phenol-type radical cations and phenoxyl-type radicals. Two different electron-transfer channels are proposed. The naphthol and hydroxybiphenyl radical cations show increased stability compared with phenol radical cations, presumably due to extensive delocalization over the whole aromatic system. 

A low molecular weight polymer with alternating ferrocene and dithiafiilvene moieties in the backbone was prepared by cycloaddition polymerization using monomer 145 as shown in Scheme 39." This polymer formed a soluble charge transfer complex with TCNQ, and on doping with iodine polymer 146 had an electrical conductivity of 3.6 X 10 S/cm. 

A much more detailed picture for a cycloaddition polymerization has been proposed by Gaylord and cowoiicers (123,124). 

Fig. 58. Mechanism of cycloaddition polymerization of dienes according to Gaylokd...

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