Deuterated styrene monomer

The samples were synthesized by the same techniques as those used for the styrene ionomers (12). The protonated styrene-methacrylic acid copolymers were prepared by thermal initiation. The polymerization took place in sealed glass tubes in the bulk at 80 °C after several freeze-thaw cycles. A conversion of 10% was obtained after 19 hr. The polymer was precipitated in methanol and neutralized in a benzene-methanol solution. A similar procedure was used for the deuterated samples except that the unreacted deuterated styrene monomer was evaporated prior to the precipitation. The mixing of the deuterated and protonated styrene copolymers was performed in a benzene solution by stirring for 1 hr. The benzene used as the solvent contained a minimum amount of methanol necessary to dissolve the ionomer (approximately 5-10% for the samples of high ion content). The samples were freeze-dried, then dried further at 60°-80°C under vacuum, and finally compression-molded at Tg - - 30°C. 

A powder scan was ran of r-dPS at room temperature, and compared with that of deuterated styrene monomer (dSM)-... 

Fig. 1. WANS spectra of deuterated at-PS (airows) and deuterated styrene monomer.

Copolymers have been prepared using (tt-CsHj )2TiCl2/AlEtj. The rates of polymerization at constant concentration of catalyst and monomer increase with increase of deuterated styrene in the monomer mixture [162], but without differences in the molecular weights of the polymers. Similar findings were obtained with the TiCl4/AlEt3(Al/Ti = 3) catalyst at 60°C [78a]. The explanation for the rate increase was considered to be an increase in the concentration of active species in the presence of the deuterated monomer. 

For all these specialty polymers, deuterium can be used as a label on one or the other monomer. Deuterium labeling allows the use of techniques based on ion detection such as forward recoil spectrometry (FRES), nuclear reaction analysis (NRA) or secondary ion mass spectrometry (SIMS). If a high-resolution depth profile of the interfacial region is needed, neutron reflectivity can also be used. The main drawback of that approach is the cost of the deuterated polymers while deuterated styrene and methyl methacrylate are expensive but commercially available, other monomers need to be synthesized and the cost can be quite prohibitive. 

Styrene-Methacrylic Acid Copolymers and Their Salts. Two different types of experiments were performed with these copolymers. A possible clustering of the ionic groups was studied with copolymers containing protonated styrene monomers and deuterated methacrylic acid groups. The radius of gyration measurements were studied from mixtures of all deuterated chains in a protonated matrix. 

In the first method, hydrogenated styrene (H-S) monomer, dlvinyl benzene (DVB), (1 mole %) and benzoin, 0.4% by weight, were subjected to free radical polymerization via UV light exposure. The synthesis was permitted to continue until about sixty to seventy per cent (60% to 70%) conversion. At that point, the remaining styrene and DVB were removed by evaporation and replaced by an exactly equal amount of deuterated styrene (D-S) and fresh DVB and initiator. The polymerization was then permitted to continue for another several per cent. Delta fraction sizes of 5 to 20% were obtained. After the delta fraction had been synthesized in place, the remaining D-S and- DVB were again removed by evaporation, and replaced by an exactly equal amount of H-S, DVB and new Initiator. Then the reaction was permitted to continue to completion via UV exposure. 

Deuterated monomers (styrene, butadiene, oxirane, hexamethylcyclotrisiloxane)... 

Zhao and Brittain [280-282] reported the LCSIP of styrene on planar silicon wafers using surface modifications of 2-(4-(ll-triethoxysilylundecyl)phenyl-2-methoxy-propane or 2-(4-trichlorosilylphenyl)-2-methoxy-d3-propane respectively. Growth of PS brushes from these SAMs has been successfully achieved factors that influence PS thickness included solvent polarity, additives and TiC concentration. Sequential polymerization by monomer addition to the same silicate substrate bearing the Hving polymer chains resulted in thicker PS films. FTIR-ATR studies using a deuterated initiator indicated that the initiator efficiency is low, and the... 

Molecular weights of polymers from styrenes deuterated in the side chain are the same as those of polystyrene prepared under the same conditions [78], and this is true also of polymers from ethylene and deuteroethylene [79]. If hydride ion transfer were rate determining an isotope effect would be expected with higher molecular weights in the deuterated polymers. The rate determining step would therefore appear to be coordination of monomer followed either by rapid transfer or insertion into the polymer chain. 

Structural studies of polymer materials often use neutron scattering techniques. In such circumstances the use of deuterated chains can be necessary because it overcomes problems associated with inelastic scattering. In this example, a commercial sample of polystyrene-d7 is polymerized in such a way as to maximize yield due to the high cost of the monomer. There is lillle advantage in polymerizing styrene in solution unless large quantities are required (where heat transfer becomes a problem). Polystyrene can be polymerized in the... 

Recently, this type of deuterated monomer method was applied to the copolymerization of MM A and styrene in the presence of BC13 at low temperature, which gives a heterotactic-rich alternating copolymer.245,246 Using styrene-/3-dj, Goto et al. revealed that the addition of MMA to the styrene radical is syndiotactic-specific while the addition of styrene to the MMA radical is isotactic-specific, and that the alternation of these addition steps gives rise to the formation of a heterotactic-rich alternating sequence. 

The sodium salt of poly(styrene sulfonate) with a narrow molecular weight distribution (PSS77, GPC standard grade, Mw 77 kg/mol) has been obtained from Fluka. The powder was evacuated to remove any residual water content. The lithium salt of poly(styrene sulfonate) (30% wt in H2O, M , 75 kg/mol) and poly(styrene sulfonic acid) (18% wt in H2O, Mw 75 kg/mol) have been purchased from Aldrich. Both samples have been concentrated in a rotary evaporator and subsequently dried under vacuum. For all experiments a concentration of 5 mmol/1 (monomer) in deuterated solvents (D2O, CD3OD and their mixtures) has been used. 

Although NMR spectroscopy is a powerful method for studying the structure of different vinyl copolymers i0l its usefulness for the olehn copolymers is rather limit The main reason is undoubtedly the strong overlap between the resonances of the main-chain protons and those of the pendant groups. Unfortunately, this situation is unlikely to be improved by increasing the spectrometer frequency. One of tte possible solutions to this problem is copolymerization with fully or partially deuterated monomers. The only exceptions to this unfortunate situation are ethylene-propylene copolymers and some styrene copolymers, and here important information about the copolymer structures was obtained, including data relevant to the mechanism of stereosp dfic polymerization (see Section IV.A.1 b). 

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