The microstructure of poly(vinylphosphonic acid) (PVPA) and poly(vinyl dimethyl phosphonate) (PVDMP) prepared by free radical polymerization was studied by a combination of one- and two-dimensional NMR spectra. Whereas 13C and 31P NMR spectra give less stereochemical information a signal split into diad, triad, and, at best, m-centered tetrad sequences for the methylene protons of PDMVP could be observed in the 1H NMR spectra. For PVPA our assignments differ from those previously published in the literature. The spectra of both polymers were complicated by the presence of head-to-head regioirregular structures with up to ∼17% for PVPA. For the regioregular part a mainly atactic structure was determined for PVPA, whereas PVDMP has an increased content of isotactic sequences. The dependency of 1H and 31P signals of PVPA on the degree of neutralization is presented.

IntroductionSince the 50s, numerous applications have been described for poly(vinylphosphonic acid) (PVPA) and its derivatives, [1][2][3] ranging from flame retardants [4,5] to cation exchange membranes, [6,7] dopants in conductive blends, [8,9] additives for coatings [10,11] or adhesion promoters in dental cements. [12] Additionally, PVPA exhibits a high solubility in water and high biocompatibility, [13] which renders a material for many other potential uses, like drug solubilization, cartilage / bone engineering or orthopaedic applications.In spite of this broad range of applications, information reported in the literature regarding synthesis and characterization of these materials is quite diffuse. Recently, however, microstructure characterization of PVPA and experimental observations characterizing the polymer as a polyelectrolyte have been reported by Bingöl et al. [14] There, it is suggested that the free radical polymerization of VPA carried out in the presence of 33 wt.-% water at 80 8C proceeds via cyclopolymerization of the vinylphosphonic acid anhydride as an intermediate.Here, we compare the polymerization of VPA in ethyl acetate and N,N-dimethylformamide (DMF) with the polymerization of VPA in acetic anhydride. Acetic anhydride Full PaperWe present the synthesis and characterization of the compounds formed in a mixture of vinylphosphonic acid (VPA) and acetic anhydride used for the radical-initiated VPA polymerization. High-molecular-weight PVPA with M w up to 109 000 g Á mol À1 was obtained from the polymerization of a mixture containing VPA, VPAAnh, VPADiAnh and their acetylated derivatives. Relative reactivities of these compounds were estimated. The resulting polymers were characterized by viscosimetry, light scattering and NMR measurements. The complexity of the polymer structure increases with increasing anhydride content in the reaction feed as can be concluded from the 1 H, 13 C and 31 P NMR spectra. This finding is in accordance with a cyclopolymerization mechanism resulting in five-and six-membered anhydride rings within the polymer chain. reacts with VPA forming different anhydride species. The reaction mixture is used for free radical polymerization and the polymerization behaviour of the different components is studied. Finally, the characterization of the resulting high molecular weight PVPAs by viscosimetry, light scattering and NMR is reported. Experimental PartMaterials VPA (BASF AG) was used as received with or without previous drying treatment (detailed below). 2,2 0 -Azoisobutyronitrile (AIBN, Aldrich) was recrystallized in methanol prior to use. Acetic anhydride (Fluka) was used without further treatment. DMF over molecular sieve (H 2 O 0.01%) was purchased from Fluka. Drying Treatment for VPAApproximately 25 g of VPA were introduced in a two-necked flask and a flow of N 2 was bubbled through at 60 8C under vacuum until volatile compounds were removed. By this procedure 5.5 wt.-% water with traces of methanol were removed from the crude monomer which was in agreement with its V...

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Structural investigations on maleic anhydride (MAn) copolymers with ethene, propene and styrene, their products of hydrolysis, and their methyl half-esters by means of I3C NMR spectroscopy are presented. The spectra of 2,3-diethylsuccinic acid and its anhydrides in the erythro-and threo-configuration and of butylsuccinic acid and its anhydride were obtained and compared with the spectra of the copolymers. In each case the results show the formation of both threo(trans)-and erythro(c~)-structures. At a polymerization temperature of 60 "C the proportions were 88% threo to 12% erythro for ethene/MAn copolymers and 80% threo to 20% erythro for propene/MAn copolymers, a ratio which was confirmed also by the hydrolyzed forms. Copolymerization at 150°C leads, in the case of propene/MAn, to 67% threo and 33% erythro. The production of ethene/MA copolymer via the copolymerization of ethene and fumaric acid half-ester and its saponification to ethene/fumaric acid leads to a ratio of 38% threo to 62% erythro. These results are in accordance with the thermal stabilities of the configurations. In the case of styrene/MAn copolymer it is not possible to obtain a unique interpretation of the configurations from the spectra. For the conversion of propene/MAn and styrene/MAn copolymers by means of methanol to half-esters it can be derived from the I3C NMR spectra how many of the half-ester moieties are obtained in the neighbourhood of the methyl and phenyl groups, respectively, of the olefin. a) Revised manuscript of August 16, 1985.