Toluene-modified copolymers

The toluene-modified copolymers containing >21% DVB quite rapidly with evolution of air bubbles-adsorb liquids such as cyclohexane and heptane which are taken up by other copolymers to a negligible extent only. At higher DVB contents the amount of organic solvent taken up is approximately equal to the amount of inert diluent originally used. In contrast to the conventional hydrocarbon copolymers, these materials can even accommodate appreciable quantities of water without observable change in volume. These phenomena can be ascribed to the existence of macropores in the copolymers containing more than 27 % DVB. 

As an alternative to networks prepared with n-decane, the toluene-modified copolymers exhibit narrower pore size distribution and smaller pore volume. A substantial part of the porous volume is provided by small voids [319] located within the initially swollen primary microgels. These pores are poorly accessible even to the small molecules of methanol. This is the reason why the surface area of the toluene-modified copolymers calculated from adsorption of methanol vapors proves to be markedly smaller than that determined by the conventional nitrogen adsorption technique [320]. In addition to micropores with a diameter below 15 A, the polymer exhibits mesopores with diameters up to 300 A, representing the space between the microgels and their aggregates. Owing to the increased portion of small pores, the surface area of the toluene-modified networks can achieve large values and exceed that of the polymen prepared with pre-cipitants [321, 315]. In order to raise both the pore volume and the pore size of solvent-modified materials, a precipitant needs to be added to toluene [322-326]. 

With respect to sweUing in non-solvents, toluene-modified styrene— DVB copolymers have much in common with hypercrosslinked polystyrenes [330]. Both are prepared in accordance with the same basic principle, the formation of rigid networks in strongly solvated state. It will be shown in detail in Chapter 7 that rigid expanded networks possess a relaxed favorable conformation only in their swollen state and, therefore, exhibit a marked tendency to acquire this state by sweUing and incorporating any liquid, even non-solvating one. 

Chem. Desap. Styrene/vinyl toluene-modified alkyd copolymer (linseed oil type) in VM P naptha (HAPS-free)... 

SiUcone-modified styrene-butyl acrylate copolymer latex was synthesised by emulsion copolymerisation using octamethylcyclotetrasiloxane(D4), styrene and butyl acrylate as raw materials, potassium persulphate as initiator and propylmethacrylate triethoxysilane as crosslinking agent. The IR spectroscopic studies showed that the vinyl monomers were completely copolymerised with D4. The prepared silicone-modified copolymer latex with the IPNs tended to have higher stability and better toluene and water resistance than styrene-butyl acrylate copolymer latex. The glossiness of coated paper was improved with silicone-modified copolymer latex and it was at a maximum when D4 was about 3% of total monomers. 16 refs. 

The use of lightly crosslinked polymers did result in hydrophilic surfaces (contact angle 50°, c-PI, 0.2 M PhTD). However, the surfaces displayed severe cracking after 5 days. Although qualitatively they appeared to remain hydrophilic, reliable contact angle measurements on these surfaces were impossible. Also, the use of a styrene-butadiene-styrene triblock copolymer thermoplastic elastomer did not show improved permanence of the hydrophilicity over other polydienes treated with PhTD. The block copolymer film was cast from toluene, and transmission electron microscopy showed that the continuous phase was the polybutadiene portion of the copolymer. Both polystyrene and polybutadiene domains are present at the surface. This would probably limit the maximum hydrophilicity obtainable since the RTD reagents are not expected to modify the polystyrene domains. 

For the synthesis of carbohydrate-substituted block copolymers, it might be expected that the addition of acid to the polymerization reactions would result in a rate increase. Indeed, the ROMP of saccharide-modified monomers, when conducted in the presence of para-toluene sulfonic acid under emulsion conditions, successfully yielded block copolymers [52]. A key to the success of these reactions was the isolation of the initiated species, which resulted in its separation from the dissociated phosphine. The initiated ruthenium complex was isolated by starting the polymerization in acidic organic solution, from which the reactive species precipitated. The solvent was removed, and the reactive species was washed with additional degassed solvent. The polymerization was completed under emulsion conditions (in water and DTAB), and additional blocks were generated by the sequential addition of the different monomers. This method of polymerization was successful for both the mannose/galactose polymer and for the mannose polymer with the intervening diol sequence (Fig. 16A,B). 

Partial hydrogenation of acetylenic compounds bearing a functional group such as a double bond has also been studied in relation to the preparation of important vitamins and fragrances. For example, selective hydrogenation of the triple bond of acetylenic alcohols and the double bond of olefin alcohols (linalol, isophytol) was performed with Pd colloids, as well as with bimetallic nanoparticles Pd/Au, Pd/Pt or Pd/Zn stabilized by a block copolymer (polystyrene-poly-4-vinylpyridine) (Scheme 9.8). The best activity (TOF 49.2 s 1) and selectivity (>99.5%) were obtained in toluene with Pd/Pt bimetallic catalyst due to the influence of the modifying metal [87, 88]. 

It appeared attractive to extend the work on emulsification of liquid-liquid systems by BG copolymers to solid-liquid systems. As a first approach a model system was studied which comprises titanium dioxide dispersed in toluene with modified styrene-butadiene block copolymers as dispersants. These studies are reported here. 

Hourston142) has studied the effect of casting solvents on some physical properties of two SBS copolymers which seem to be Kraton 1101 and 1102. The properties of films cast from cyclohexane solution were found to be independent of the evaporation rate while those of films cast from toluene solution were found to be modified by the evaporation rate. 

Triphenylmethyl methacrylate (TrMA) and azobenzene-modified methacrylates were randomly copolymerized in toluene at — 78°C with chiral catalysts to give optically active helical copolymers (19 in Fig. 6) [65]. The optical activity (optical rotation) of the copolymers decreased with the increasing content of the azobenzene-modified methacrylates in the copolymers. The single helical conformation of PTrMA is quite stable in solution, but the copolymers of TrMA with less bulky methacrylates cannot keep their helical structure and lose their optical activity during the polymerization or after the polymerization in solution, which is highly dependent on the bulkiness of the comonomers [22]. The copolymer (19 x = 2) containing 26 mol% azobenzene units, also lost its optical activity upon irradiation within 20 min. This change is due to the helix-to-coil transition of the copolymer and can occur in the dark. 

Similar to the case of styrene, the copolymers of alkylstyrenes and arylstyrenes are common. The copolymerization is done for the same purposes as for polystyrene, namely to improve/modify certain properties. Copolymerization with divinylbenzene is probably the most frequently utilized. This copolymerization improves mechanical resistance, decreases solubility, and improves thermal resistance. For example, thermal decomposition of poly(vinyltoluene-co-divinyl benzene) 10-50% DVB starts at a higher temperature than that of poly(vinyl toluene). The decomposition at 560° C generates C1-C4 hydrocarbons, benzene, toluene, ethylbenzene, styrene, ethyltoluene, a-methylstyrene, vinyltoluene, divinylbenzene, naphthalene, and ethylstyrene, with a distribution that varies with copolymer composition [71, 118]. 

Beiner et al. modified a divinylbenzene/A-vinyl pyrrolidone copolymer, containing sulfonic acid groups, with several metal ions. The modified cation-exchange material was used for the extraction of thiols, sulfides, and methyl thiophosphates from water samples, with LODs in the upper ng/1 range after elution with a CSi/toluene mixture and analysis by GC/MS. 

Usually the silica/polymer composites are prepared with styrene, MMA, BA, or their copolymers. However, few reports cover experiments with less commonly used polymers such as poly(styrene sulfonic acid) (PSSA), poly(hydroxyethylmethacry-late) (PHFMA), poly(aminoethylmethacrylate) PAEMA [133], polyethylene (PE) [134], or polyamides [135]. Using a miniemulsion of nickel-based catalysts for the polymerization of ethylene, which is dispersed in toluene in the presence of hy-drophobically modified silica particles, PEysilica hybrids could be prepared [134]. The ethylene is introduced into the system by bubbling through the miniemulsion. The hydrophobic moiety of the silica particles interacts with the growing polymer and leads to lentil-shaped or isotropic hybrids. Lentil-shaped particles are composed of semicrystalline PE, whereas the isotropic hybrids are composed of amorphous polymer. The crystallinity of the polymer is determined by the choice of polymerization catalyst. Silica/polyamide hybrid nanoparticles were prepared with 3-aminopropyltriethoxysilane (APS)-modified silica particles [135]. These particles were dispersed in sebacoylchloride and the solution miniemulsifled in an aqueous... 

Toluene-2,6-diisocyanate sealant modifier, solvent-based weatherable Styrene-ethylene-propylene block copolymer sealant, automotive Toluene bis (dimethyl urea) sealant, canal walls Bentonite sealant, casting... 

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