Phase-transfer catalysis polymer synthesis

Nava, H. and Percec, V., Functional polymers and sequential copolymers by phase-transfer catalysis. 18. Synthesis and characterization ofa,co-bis(2,6-dimethylphenol)-poly(2,6-dimethyl-1,4-phenylene oxide) and a,Q)-bis(vinylbenzyl)-poly (2,6-dimethyl-1,4-phenylene oxide) oligomers. J. Polym. Sci., Part A Polym. Chem., 1986. 24(5) p. 965-90. 

CM Starks, Phase Transfer Catalysis in Organic and Polymer Synthesis. Mechanism and Synthesis. (ed. ME Halper) ACS Symposium Series 659, Am. Chem. Soc., Washington, 1997. 

New Developments in Polymer Synthesis by Phase-Transfer Catalysis... 

A series of polyphosphites, polyphosphates, polythiophosphates, and other polymers containing sulfone functions, based on 1, have also been described [17,119]. An efficient synthesis of polyethers from 1 and 1,8-dibromo or dimesyl octane by microwave-assisted phase transfer catalysis has been reported [120]. 

Polymeric phosphonium salt-bound carboxylate, benzenesulphinate and phenoxide anions have been used in nucleophilic substitution reactions for the synthesis of carboxylic acid esters, sulphones and C/O alkylation of phenols from alkyl halides. The polymeric reagent seems to increase the nucleophilicity of the anions376 and the yields are higher than those for corresponding polymer phase-transfer catalysis (reaction 273). 

THE SYNTHESIS OF HYDROPHOBE-MODIFIED HYDROXYETHYL CELLULOSE POLYMERS USING PHASE TRANSFER CATALYSIS... 

This paper describes our efforts to apply phase transfer catalysis (PTC) to the synthesis of HMHEC polymers. The potential use of PTC in the manufacture of HMHEC polymers is important because a large portion of the manufacturing cost of HMHEC polymers is the cost of the hydrophobe reactant. Higher alkylation efficiencies would increase the overall reaction efficiency and thus reduce the overall cost of the final HMHEC product. Increased hydrophobe alkylation efficiencies would also reduce the volume of unreacted hydrophobe in the waste stream and reduce disposal costs. 

Table 2. Synthesis of HMHEC polymers by phase transfer catalysis from CELLOSIZE HEC QP-300...

Yanagida, S., K. Takahashi, and M. Okahara, Solid-Solid-Liquid Three Phase Transfer Catalysis of Polymer Bound Acyclic Poly(oxyethylene) Derivatives Applications to Organic Synthesis, ... 

The synthesis of poly(ether imide)s by condensation of the disodium salt of bisphenol-A with bis(chlorophthalimide)s under microwave irradiation conditions has been described by Zhang et al. (Scheme 14.21) [50]. The polymerization reactions were performed under phase-transfer catalysis (PTC) conditions in o-dichlorobenzene solution. For this purpose a mixture of 16.12 mmol bis(chloro-phthalimide)s and 16.12 mmol disodium salt of bisphenol-A in 60 mL o-dichlorobenzene with 0.56 mmol hexaethylguanidinium bromide was irradiated in a domestic microwave oven for 25 min and the product was precipitated by addition of methanol. The polymerization reactions, in comparison with those under the action of conventional heating, proceeded rapidly (25 min compared with 4 h at 200 °C) and polymers with inherent viscosities in the range 0.55 to 0.90 dL g were obtained. 

Leznoff has published further on the solid-phase synthesis of insect sex attrac-tants. The advantages and uses of enzymes attached to solid supports have been reviewed. Aspects of triphase catalysis (organic layer-water-polymer) have been discussed by Regen, while advances in phase-transfer catalysis have been reviewed. A crown ether NAD(P)H mimic has been described,bringing synthetic chemists nearer to the objective of artificial enzyme systems. 

The fundamental theory of phase transfer catalysis (PTC) has been reviewed extensively. Rather than attempt to find a mutual solvent for all of the reactive species, an appropriate catalyst is identified which modifies the solubility characteristics of one of the reactive species relative to the phase in which it is poorly solubilized. The literature on the use of PTC in the preparation of nitriles, halides, ether, and dihalocarbenes is extensive. Although PTC in the synthesis of C- and 0-alkylated organic compounds has been studied, the use of PTC in polymer synthesis or polymer modification is not as well studied. A general review of PTC in polymer synthesis was published by Mathias. FrecheE described the use of PTC in the modification of halogenated polymers such as poly(vinyl bromide), and Nishikubo and co-workers disclosed the reaction of poly(chloromethylstyrene) with nucleophiles under PTC conditions. Liotta and co-workers reported the 0-alkylation of bituminous coal with either 1-bromoheptane or 1-bromooctadecane. Poor 0-alkylation efficiencies were reported with alkali metal hydroxides but excellent reactivity and efficiencies were found with the use of quaternary ammonium hydroxides, especially tetrabutyl- and tetrahexylammonium hydroxides. These results are indeed noteworthy because coal is a mineral and is not thought of as a reactive and swellable polymer. Clearly if coal can be efficiently 0-alkylated under PTC conditions, then efficient 0-alkylation of cellulose ethers should also be possible. 

There has recently been great interest in the synthesis of dendritic polymers, although applications of these have so far been few [59]. The first report of a reaction where a dendrimer is actually catalytic involved a biphasic system similar to phase transfer catalysis. The quaternary ammonium ion dendrimer (Figure 5.26) has 36 trimethylammonium functions, and catalyses the unimolecular decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, and the hydrolysis of 4-nitrophenyldiphenyl phosphate [60]. 

The technique of phase transfer catalysis is now twenty-five years old and has come of age. It has been applied to many areas of organic synthesis, from small and simple molecules to large and complex polymers. Successful chiral catalysts are beginning to be reported [61], and industry is starting to embrace phase transfer methods [62]. Phase transfer catalysis clearly has an important role to play in a cleaner future. 

Two new synthetic methods for the preparation of functional polymers containing 2-oxazoline pendant groups were developed. The first concerns the synthesis of m- and p-vinylbenzyl ethers of 2-(p-hydroxyphenyl)-2-oxazoline, followed by their radical poljnnerization. 2-(p-Hydroxyphenyl)-2-oxazo-line was reacted with a mixture of m- and p-chloromethylstyrene (60% m and 40% p) under phase transfer catalysis conditions at room temperature. The m-and p-vinylbenzyl ethers of 2-(p-hydroxyphenyl)-2-oxazoline obtained were separated by selective crystallization from methanol. Radical polymerization of these ethers was carried out in dioxane at 60 C, giving polymers with pendant 2-oxazoline groups. 

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