Chloromethyl Substituted Polystyrene

Reproduced with permission from H. Nakagawa, S. Tsuge, S. Mohanraj and W.T. Ford, Macromolecules, 1988, 21, 930. 1988, American Chemical Society [18] 

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Modifications of chloromethyl substituted polystyrene and poly(vinyl halides). 

Chloromethyl substituted polystyrenes can also be prepared from poly(p-methyl styrene)s by treating them with aqueous sodium hypochlorite in the presence of a phase transfer catalysts, like benzyltriethylammonium chloride. The conversions of methyl to chloromethyl groups can be as high as 20% without any detectable formation of dichloromethyl groups. When, however, the reactions are pushed to conversions as high as 61%, some dichloromethyl groups form. 

Nakagawa and co-workers [18] used techniques based on high resolution Py-GC and Py-GC and TGA to measure thermal degradation of chloromethyl substituted polystyrene. A typical TGA weight loss curve is shown in Figure 4.1. Degradation starts at 200 "C and peaks at 400 °C. Typical pyrolysis products of chloromethylated styrene-divinyl benzene (St-DVB) copolymers are the monomers, dimers and trimers of styrene, p-methyl styrene, and divinyl and ethyl styrene. For styrene chloromethyl St-DVB copolymers, in addition to the above, /-methyl styrene monomer and m- and p-chloromethyl styrene monomers are also present in pyrolysates. 

Methods for obtaining structural information on these chloromethyl substituted polystyrenes are discussed next. 

Due to its ready availability, high reactivity and other interesting properties, chloromethyl substituted polystyrene (I) has been the most extensively studied substrate in chemical modification via phase transfer catalysis. Reactions have been carried out both on soluble poly(chloromethyl styrene) (Ref. 12,... 

Chloromethyl-substituted polystyrene gels usnally crosslinked with divinylbenzene (DVB) are widely used as key intermediates for ion-exchange resins, supports for solid-... 

Bio-beads consists of (1% cross-linked polystyrene with 1.25 mmol chloromethyl substitution per gram of dry resin respectively benzhydrylamine polymer (1% cross-linked polystyrene with 0.24 mmol NH2 per gram of dry resin, Bio-Rad Laboratories (Richmond, CA, USA). 

In the initial step, the first BOC-protected amino acid is bound to the polymer, e.g. polystyrene in which a proportion of the phenyl rings have chloromethyl substitution. Attachment to these residues is through the carboxyl via an ester linkage. This involves a simple nucleophilic substitution reaction, with the carboxylate as nucleophile and chloride as leaving group (see Section 6.3.2). After each stage, the insoluble polymer-product combination is washed free of impurities. 

Treatment with a deficient quantity of chlorobis(cyclooctene)rhodium(I) dimer (Scheme 3) after 12 h gave a shell of rhodium near the surface. With excess reagent after 4 days the rhodium was incorporated uniformly. Cyclopentadienyltitanium catalysts bound to 2% and 20% cross-linked macroporous polystyrenes had uniform titanium distribution when initially functionalized by chloromethylation (22). Surface binding of Pd from (PhCN)2PdCl2 on 2% cross-linked, tertiary amine-substituted polystyrene was found by X-ray photoelectron spectroscopy (2S). 

Methods are now available for the synthesis of N substituted monoaza-crowns with >N(CH2CH20)jj-H sidearms (31). Such molecules could be attached to chloromethylated polystyrene as indicated in references 35-50. 

Aromatic electrophilic substitution is used commercially to produce styrene polymers with ion-exchange properties by the incorporation of sulfonic acid or quaternary ammonium groups [Brydson, 1999 Lucas et al., 1980 Miller et al., 1963]. Crosslinked styrene-divinyl-benzene copolymers are used as the starting polymer to obtain insoluble final products, usually in the form of beads and also membranes. The use of polystyrene itself would yield soluble ion-exchange products. An anion-exchange product is obtained by chloromethylation followed by reaction with a tertiary amine (Eq. 9-38) while sulfonation yields a cation-exchange product (Eq. 9-39) ... 

We note from Table VIII a strong interest in halogenated resists, particularly those substituted with chlorine. The addition of chlorine to the aromatic structure of polystyrene has a marked effect on cross-linking efficiency. Monodisperse polystyrene, for example, has a sensitivity on the order of 50 p C/cm2, yet with as little as 20% chloromethyl groups substituted on the ring, the sensitivity is improved to 2 C/cm2 for comparable molecular weight and distribution. 

Chloromethyl polystyrene can be converted to a free-radical initiator by reaction with 2,2,6,6-tetramethylpipcridinc-/V-oxyl (TEMPO). Radical polymerization of various substituted alkenes on this resin has been used to prepare new types of polystyrene-based supports [123]. Alternatively, cross-linked vinyl polystyrene can be copolymerized with functionalized norbornene derivatives by ruthenium-mediated ringopening metathesis polymerization [124],... 

Hydroxymethyl polystyrene has been prepared from chloromethyl polystyrene, either by conversion into the acetate by nucleophilic substitution followed by saponification, or directly by treatment with a mixture of potassium acetate and tetrabutyl-ammonium hydroxide in 1,2-dichlorobenzene/water (85 °C, 2 d [61]). 

Various thiamine derivatives were prepared on polymer support and were tested in C-C coupling reactions.40 The most straightforward approach was the alkylation of substituted 1,3-thiazoles with chloromethyl polystyrene resin yielding supported thiazolium chloride salts. Alternatively, resin-supported thiamine derivatives were constructed in a two-step process by alkylation of the primary alcohol with chloromethyl polystyrene followed by alkylation of the ring nitrogen yielding resin 12 (Fig. 8). Not only does this pathway introduce a spacer between the active thiamine... 

Chloromethylated polystyrene 4-aminophenyl-substituted porphyrin Tangestaninejad and Mirkhani (118)... 

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