Vinyl alcohol block copolymers

Hydrolysis of the trialkyl silyl groups gives poly(vinyl alcohol). Block copolymers in which one block is poly( vinyl alcohol) can be synthesized if a telechehc with an aldehyde terminal group is used to initiate the aldol GTP structures such as polyfsty-rene-h/oc -vinyl alcohol) can be prepared in this way. Alternatively, as silyl ketene acetals can react with aldehydes, block structures can be formed by a coupling process. 

Investigations were mainly devoted to the synthesis of telechelic polymers and copolymers rather than to living radical polymerization. In particular, from 1960, Imoto et al. [234] started surveys on the synthesis of block copolymers from this method. Thus, polystyrene-i>-poly(vinyl alcohol) diblock copolymer... 

Crystallization of cis—1,4-polyisoprene from solution at -65 C has been carried out it is therefore possible that block copolymer preparation by epoxidation, bromination or some other reaction could be accomplished with lamellas of this polymer. Lamellar crystallization of cellulose, of amylose and of polyacrylic acid have been reported substitution reactions such as acetylation or ether formation with the hydroxyl groups and esterfication of the acid groups are possible reactions to carry out with lamellas of those polymers. The use of nonaqueous systems may be better suited to prevent swelling, and therefore, attack of the crystalline regions. It should also be possible to react poly(vinylalcohol) lamellas in suspension with acids or anhydrides to form vinyl-alcohol-vinyl ester block copolymers or with phosgene to obtain chloroformate groups which can undergo further reactions. 

Matsumura, S. and Tanaka, T. (1994) Novel malonate-type copolymers containing vinyl alcohol blocks as biodegradable segments and their builder performance in detergent formulations. J. Environ. Polym. Degrad.,... 

Fig. 3. Influence of vinyl alcohol—vinyl acetate copolymer composition on melting temperature (56), where A represents block copolymers B, blocky...

In a previous paper (15) the segment density of PVA adsorbed on PS latex in water was presented and it was noted that H Cgans was at the extremity of the s.a.n.s. profile. Calculating <5 assuming a value of a of 0.5 nm gives 13 nm in contrast to the experimental value of 18 nm. The discrepancy here is much smaller than in the case of PE0. This effect is difficult to interpret without further theoretical work but may be attributable to the fact that the PVA chain is less flexible than PEO and that the block structure (PVA is a random block copolymer of vinyl acetate. 12%, and vinyl alcohol) makes the formation of tails less likely. 

Scheme 9.8 Semihydrogenation of olefin alcohols with Pd colloids stabilized by a block copolymer polystyrene-poly-4-vinyl pyridine.

Polyurethane block copolymer with polyether/polyester Poly(vinyl alcohol)... 

The copolymerization product was soluble in DMF and in chloroform. When the reaction was complete the product was precipitated with methanol, redissolved in chloroform, reprecipitated with methanol, and then dried. Hydrolysis of the copolymer followed by separation and analysis shows that one of the products of the hydrolysis is poly(vinyl alcohol) with molecular weight similar to that of the initial PVA. All these findings lead to the conclusion that by the copolymerization of two different multimonomers a copolymer with two ladder-type blocks can be obtained. However, the possibility that the copolymer is slightly branched cannot be excluded, and the assumption that mainly ladder-type, linear structure exists still needs confirmation. 

HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HNS NTO NTO/HMX NTO/HMX NTO/HMX PETN PETN PETN PETN PETN PETN PETN PETN PETN PETN RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX TATB/HMX Cariflex (thermoplastic elastomer) Hydroxy-terminated polybutadiene (polyurethane) Hydroxy-terminated polyester Kraton (block copolymer of styrene and ethylene-butylene) Nylon (polyamide) Polyester resin-styrene Polyethylene Polyurethane Poly(vinyl) alcohol Poly(vinyl) butyral resin Teflon (polytetrafluoroethylene) Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Cariflex (block copolymer of butadiene-styrene) Cariflex (block copolymer of butadiene-styrene) Estane (polyester polyurethane copolymer) Hytemp (thermoplastic elastomer) Butyl rubber with acetyl tributylcitrate Epoxy resin-diethylenetriamine Kraton (block copolymer of styrene and ethylene-butylene) Latex with bis-(2-ethylhexyl adipate) Nylon (polyamide) Polyester and styrene copolymer Poly(ethyl acrylate) with dibutyl phthalate Silicone rubber Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Epoxy ether Exon (polychlorotrifluoroethylene/vinylidine chloride) Hydroxy-terminated polybutadiene (polyurethane) Kel-F (polychlorotrifluoroethylene) Nylon (polyamide) Nylon and aluminium Nitro-fluoroalkyl epoxides Polyacrylate and paraffin Polyamide resin Polyisobutylene/Teflon (polytetrafluoroethylene) Polyester Polystyrene Teflon (polytetrafluoroethylene) Kraton (block copolymer of styrene and ethylene-butylene)... 

Figure 8. Dependence of dextrin hydrolysis rates (v) on the substrate concentration in the presence of the block copolymer at 70°C. [Catalyst] = 1.00 X 10 2N. Catalyst (mole ratio of vinyl alcohol to styrenesulfonic acid units in the copolymer) (O) sulfuric acid (%) block copolymer No. 1 (1-4) (A) block copolymer No. 2 (9.8) (A) block copolymer No. 3 (22.1).

PS PSF PSU PTFE PU PUR PVA PVAL PVB PVC PVCA PVDA PVDC PVDF PVF PVOH SAN SB SBC SBR SMA SMC TA TDI TEFE TPA UF ULDPE UP UR VLDPE ZNC Polystyrene Polysulfone (also PSU) Polysulfone (also PSF) Polytetrafluoroethylene Polyurethane Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) poly(vinyl butyrate) Poly(vinyl chloride) Poly(vinyl chloride-acetate) Poly(vinylidene acetate) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl fluoride) Poly(vinyl alcohol) Styrene-acrylonitrile copolymer Styrene-butadiene copolymer Styrene block copolymer Styrene butadiene rubber Styrene-maleic anhydride (also SMC) Styrene-maleic anhydride (also SMA) Terephthalic acid (also TPA) Toluene diisocyanate Ethylene-tetrafluoroethylene copolymer Terephthalic acid (also TA) Urea formaldehyde Ultralow-density polyethylene Unsaturated polyester resin Urethane Very low-density polyethylene Ziegler-Natta catalyst... 

The membrane used depends on the nature of the organics. Poly(vinyl alcohol) and cellulose acetate [14] have been used to separate alcohols from ethers. Polyurethane-polyimide block copolymers have been used for aromatic/aliphatic separations [17]... 

The interfacial properties of an amphiphilic block copolymer have also attracted much attention for potential functions as polymer compatibilizers, adhesives, colloid stabilizers, and so on. However, only a few studies have dealt with the monolayers o well - defined amphiphilic block copolymers formed at the air - water interface. Ikada et al. [124] have studied monolayers of poly(vinyl alcohol)- polystyrene graft and block copolymers at the air - water interface. Bringuier et al. [125] have studied a block copolymer of poly (methyl methacrylate) and poly (vinyl-4-pyridinium bromide) in order to demonstrate the charge effect on the surface monolayer- forming properties. Niwa et al. [126] and Yoshikawa et al. [127] have reported that the poly (styrene-co-oxyethylene) diblock copolymer forms a monolayer at the air - water... 

However, in a recent publication, Shirinyan, Mnatsalianov, et al. (20) find that differences between the rates of vinyl acetate emulsion polymerisation observed with samples of similar polyvinyl alcohols manufactured by the same process In three different factories could be attributed to a condensation product of acetaldehyde derived from hydrolysis of residual vinyl acetate this gave rise to a conjugated ketone type ultra-violet spectrum and could be extracted from the polyvinyl alcohol under suitable conditions. This could be the uncontrolled factor which appears to have confounded nmuiy of the experiments reported here. Even more recently the same laboratory ( ) has reported that there Is an optimum sequence length of hydroxyl groups in the polyvinyl cdcohol-acetate block copolymer for polymerisation rate and dispersion stability. 

Tuzar and Kratochvil (23) have reported that styrene-butadiene block copolymers mlcellise in selective solvents for polystyrene and solubilise large amounts of polybutadiene homopolymer. Sinc.e the surface active grades of polyvinyl alcohol are polyvinyl alcohol-acetate block copolymers and water is a selective solvent for polyvinyl alcohol a similar effect may be expected which could affect the course of the vinyl acetate emulsion polymerisation. 

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