MODIFICATION substituted polymers, preparation

Random copolymers of acrylamide with N,N-dimethylacrylamide and with N,N-diethylacrylamide were prepared as illustrated in reactions (7) and (8). The respective copol3nners, PAMDMAM and PAMDEAM, have been synthesized to elucidate more fully the role of hydrogen-bonding and N-substitution on viscosity modification. These polymers were synthesized using potassium persulfate initiators in water or 30% methanol/water solutions. Reaction conditions and monomer feed ratios are given in Table 2. The resulting copolymers were purified by precipitation into acetone followed by vacuum drying at 50 C for 60 hours. 

The Curtius rearrangement procedure described here is a modification of one reported by Winestock. The submitters have found this procedure to be considerably more reproducible when N,N-diisopropylethylamine is substituted for triethylamine. The procedure described for the preparation of trans-2,4-pentadienoic acid is a modification of an earlier one by Doebner. The submitters have found this method to give reproducibly higher yields, and to be more convenient, than other commonly used procedures for preparing this material. The use of dichloromethane as the extracting and crystallizing solvent greatly simplifies the isolation of polymer-free samples of the crystalline acid. 

In spite of the fact that the preparation of polydichlorophosphazene nowadays can be reached in many different ways and with great efficiency (vide supra), the substitution of the chlorine atoms of this polymer to form stable poly-(organophosphazenes) is stiU a source of problems as it can be seldom driven to completeness and a very small amount of unreacted chlorines is always present in the final phosphazene material [38]. The complete ehmination of these chlorines is mandatory if the modification of the phosphazene materials over time has to be successfully prevented. 

Moreover it has been shown that PV0CC1 prepared by free-radical polymerization of vinyl chloroformate (V0CC1) is an atactic polymer having a Bernouillian statistical distribution as expected (J[9). In order to extend our studies on the chemical modification of PV0CC1, the stereoselective character of the nucleophilic substitution of the chloroformate units with phenol has been examined by the study of the 13c-NMR spectra of partly modified polymers in the region of the aliphatic methine carbon atoms. The results obtained in this field are presented here. 

Chemical modifications of PPO by electrophilic substitution of the aromatic backbone provided a variety of new structures with improved gas permeation characteristics. It was found that the substitution degree, main chain rigidity, the bulkiness and flexibility of the side chains and the polarity of the side chains are major parameters controlling the gas permeation properties of the polymer membrane. The broad range of solvents available for the modified structures enhances the possibility of facile preparation of PPO based membrane systems for use in gas separations. 

Reverse-phase HPLC (RP-HPLC) separates proteins on the basis of differences in their surface hydophobicity. The stationary phase in the HPLC column normally consists of silica or a polymeric support to which hydrophobic arms (usually alkyl chains, such as butyl, octyl or octadecyl groups) have been attached. Reverse-phase systems have proven themselves to be a particularly powerful analytical technique, capable of separating very similar molecules displaying only minor differences in hydrophobicity. In some instances a single amino acid substitution or the removal of a single amino acid from the end of a polypeptide chain can be detected by RP-HPLC. In most instances, modifications such as deamidation will also cause peak shifts. Such systems, therefore, may be used to detect impurities, be they related or unrelated to the protein product. RP-HPLC finds extensive application in, for example, the analysis of insulin preparations. Modified forms, or insulin polymers, are easily distinguishable from native insulin on reverse-phase columns. 

When two polymeric systems are mixed together in a solvent and are spin-coated onto a substrate, phase separation sometimes occurs, as described for the application of poly (2-methyl-1-pentene sulfone) as a dissolution inhibitor for a Novolak resin (4). There are two ways to improve the compatibility of polymer mixtures in addition to using a proper solvent modification of one or both components. The miscibility of poly(olefin sulfones) with Novolak resins is reported to be marginal. To improve miscibility, Fahrenholtz and Kwei prepared several alkyl-substituted phenol-formaldehyde Novolak resins (including 2-n-propylphenol, 2-r-butylphenol, 2-sec-butylphenol, and 2-phenylphenol). They discussed the compatibility in terms of increased specific interactions such as formation of hydrogen bonds between unlike polymers and decreased specific interactions by a bulky substituent, and also in terms of "polarity matches" (18). In these studies, 2-ethoxyethyl acetate was used as a solvent (4,18). Formation of charge transfer complexes between the Novolak resins and the poly (olefin sulfones) is also reported (6). 

The conventional methods for the synthesis of organosilanols can be accomplished by the hydrolysis of the appropriate substituted silane in the presence of catalysts such as an acid or a base.1 This synthetic route, however, had some difficulty when applied to the synthesis of silanol polymers which demanded not only high conversion of the functional groups for polymer modification but also resistance to the transformation of silanols to siloxane by self- or catalytic condensation during the preparation. 

The t-BOC protected copolymers were prepared both by copolymerization of the t-BOC protected hydroxyphenylmaleimide monomer with styrene and by modification of preformed phenolic copolymers of various molecular weights as shown in Scheme I. In both cases the copolymer compositions were foxmd to be 1 1 based on NMR results and elemental analyses. The NMR and IR spectra obtained from copolymers from both routes were identical. The 13C and IH NMR spectra of the modified polymer are shown in Figures 1 and 2. These data substantiate the completeness of the protection reaction of the preformed phenolic copolymer. The copolymers are presumed to be predominately alternating since these comonomers represent an example of the classic general alternating copolymerization case of an electron rich comonomer (styrene) and an electron poor comonomer (N-substituted maleimide) (13). 

Another approach to the preparation of polymer-supported metal Lewis acids is based on polymerization of functional monomers. If synthesis of the functional monomer is not difficult, polymerization should afford structurally pure functional polymers, because the polymer formed requires no further complicated chemical modification. A variety of substituted styrene monomers are now commercially available styrene monomers with an appropriate ligand structure can be prepared from these. Several other interesting functional monomers such as glycidyl methacrylate, 2-hydr-oxyethyl methacrylate, and other acrylics have also been used extensively to prepare functional polymers. 

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