PVAc—See Poly

Giguere and Mayer [121] reported on the dissociation of gas-phase poly(vinyl acetate) (PVAc), see Figure 21, ionised by Li+ investigated by electrospray-ionisation (ESI) mass and collision induced dissociation (CID) mass spectrometry. 

High-pressure static and dynamic light scattering were used to closely examine the behavior of block copolymers of poly(vinyl acetate) (PVAc) and poly(l,l,2,2-tetrahydroperfluoroalkyl acrylate (PTAN) as a function of C02 density (Buhler et al., 1998). The phase diagram for PVAc-6-TAN shows three distinct phases as a function of polymer concentration and C02 density at a fixed temperature of 45 °C (see Figure 9.1). The block copolymer forms a precipitated phase at low C02 densities, spherical micelles at intermediate C02 densities, and unimers, or free polymer chains in solution, at high densities. The micelles-to-unimer transition was found to be very... 

Miyashita et al. carried out miscibility characterization of CA blends with poly(N-vinyl pyrrolidone) (PVP), poly(vinyl acetate) (PVAc), and poly(N-vinyl pyrrolidone-co-vinyl acetate) random copolymers [P(VP-co-VAc)s] [ 104]. On the basis of thermal transition data obtained by differential scanning calorimetry (DSC), a miscibility map (Fig. 8) was completed as a function of the degree of substitution (DS) of CA and the VP fraction in P(VP-co-VAc). Figure 9 compares results of the DSC measurements between two blending pairs of CA/P(VP-co-VAc) corresponding to the polymer combinations marked as A and B in Fig. 8. In the data (Fig. 9b) for the blends of CA (DS = 2.95) with P( VP-co-VAc) of VP = 51 mol %, we can readily see a sign of poor miscibility, as is evidenced from the lack of an appreciable shift in the... 

Moreover, the reactivation of a cobalt-terminated polymer in the presence of second monomer leads to block copolymerization. In this respect, CMRP has aheady contributed to the preparation of the valuable copolymers listed in Table 4.1. For example, well-defined poly(acrylate) block copolymers were prepared via a sequential polymerization of acrylic monomers with cobalt porphyrin la or cobaloximes 2 [14, 20]. The synthesis of well-defined poly (acrylate)-b-poly(VAc) block copolymers was also achieved with complex la [26]. Co(acac)2 (3a see Figure 4.1) is the most prolific complex for the preparation of block copolymers, until now. Indeed, the sequential CMRP of VAc with NVP [33], AN [48], or vinyl pivalate (VPi) [49] leads to the corresponding block copolymers, in controlled fashion. Throughout the polymerization, the experimental conditions were necessarily adjusted, taking into consideration the reactivity of the second monomer. As an illustration of this, well-defined PVAc-b-poly(acrylonitrile) (PAN) copolymers could only be prepared via a bulk polymerization of VAc at 30 °C, followed by the AN polymerization at 0°C in solution in DMF [48]. In this case, the DMF not only serves as the solvent but also binds the metal and adjusts its reactivity. As a rule, the PVAc sequences of these copolymers were hydrolyzed in order to provide poly(vinyl alcohol) (PVA)-containing derivatives, such as hydrosoluble PVA-b-poly... 

Hydroxyl groups in polymer chains impart hydrophilicity and water-solubility to the polymer. They form strong hydrogen bonds which increase the T of the polymers. Ester side group polymers can be polyacrylic acid esters, polymethacrylic acid esters, or esters of poly(vinyl acetate) (PVAc), see Figure 6.15. 

It has been known for some time [see Ref. (176) for earlier work] that if poly(vinyl alcohol), produced by hydrolysis of poly(vinyl acetate) is reacetylated, the PVAc so obtained has a lower MW than the original PVAc prior to hydrolysis, though the MW of the material is not lowered any further by subsequent cycles of hydrolysis and reacetylation. Various explanations had been advanced for this phenomenon Wheeler explained it as a consequence of the presence of branches joined to the main chain through ester linkages which would be broken on hydrolysis and not re-formed on reacetylation. These branches were ascribed to chain transfer reactions with acetate groups, either in the polymer, or in monomer molecule subsequently polymerized at their double bonds. Transfer reactions by attack on hydrogen atoms other than those in... 

In the vicinity of glass transition, both Eqs. (47) and (48) become Eqs. (42) and (43), respectively. The calculated dependence of the physical aging rate on temperature for polystyrene (PS), poly(vinyl chloride) (PVC), and poly(vinyl acetate) (PVAc) is shown in Fig. 17. There are five parameters (e, p, f xr, 7 ) in Eqs. (23), (2), (15) and (19). We have chosen p = 1/2. ft = 1/30, and xr = 30 min for these linear polymers in our theoretical calculation. The other two parameters r. = h and Tr are listed in Table 1. The calculation reveals that the Struik exponent (p) increases from zero above 7 to a constant below Tg, and then decreases to zero at 200 K below Tg. The three polymers all show a similar type of temperature dependence of physical aging rate, which compares well with the reported observations (see Fig. 15 of Ref. 2). 

Direct insertion probe mass spectrometry (DIP-MAS) analyses of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), and their coalesced and precipitated blends were performed [51] (see Fig. 21). The fact that the pyrolysis mass... 

Vilanove and Rondelez11 measured the surface osmotic pressure of a polymer as a function of concentration. They used poly-vinyl acetate (PVAc) spread on an air-liquid interface. They determined the osmotic pressure by using the Wilhelmy method (see Section 1.10). 

Figure 7.9. Dependence of the melt viscosity rj of polymers on the parameter Zw (see text) at 021 0. For easier comparison, the 17 values of the different types of polymer have all been multiplied by a constant factor of C. PDMS, Poly(dimethyl siloxane) PIB, poly(isobutylene) PB, poly(butadiene) PMMA, poly(methyl methacrylate) PVAC, poly(vinyl acetate) PS, poly(styrene) (after T. G. Fox).

However, the presented cement-in-polymer dispersions usually contain up to 20 wt-% of the polymer. It is, therefore, not surprising to see a pronounced influence of the polymer on the pull-out performance in Fig. 1. Although both coated rovings clearly outperform the uncoated one, the roving coated with the cement-in-poly(vinyl alcohol), c/PVA, fails at approximately half the load of the cement-in-poly(vinyl acetate), c/PVAc. The reason for this is likely to come from the differences in the chemical and physical properties of the polymers. 

Figure 3.25 shows the changes of heat capacity with temperature for the polyepichlorohydrin (PECH)/poly(vinyl acetate) (PVAc) combination at different diffusion times. In the glass transition region, the heat capacity traces are different for the different diffusion times.However, it is difficult to draw out more detailed information from these traces. The dCp/dT curves, however, clearly showed that an interface is formed by thermal diffusion, (see Figure 3.26). This is shown by the increase in the dCp/dT signal between the two glass transitions. With increasing diffusion time, the concentration of the interface will change and its thickness will increase.

To evaluate this model, an experiment with a four-component system was conducted This system was a poly(methyl acrylate)/poly(vinyl acetate) (PMA/PVAc) physical blend, or mixture, consisting of four individual blends (PMA/PVAc (80/20) + PMA/PVAc (60/40) + PMA/PVAc (40/60) - -PMA/PVAc (20/80)). PMA is miscible with PVAc. The open squares in Figure 3.49 are the experimental dCp/dT data. The difference between glass transition temperatures of PMA and PVAc is about 33°C. In the glass transition region, the four-component mixture showed an acceptable fit to the experimental data, see Figure 3.49. The solid lines shown in Figure 3.49... 

It is often desirable to perform some kind of chemical modification to polymers once they have formed. Acetylation of cellulose, for example, represents the chemical modification of a naturally occurring polymer (see chapter 3) to give the technologically useful cellulose diacetate and triacetate polymers. Poly(vinyl alcohol) (PVA) is a well-known example of a polymer that can only be formed by chemical modification since vinyl alcohol monomer does not exist (except as its keto form, acetaldehyde). Instead, PVA is formed by hydrolysis of poly(vinyl acetate) (PVAc). Partly hydrolysed PVAc is, of course, simply a copolymer of VA and VAc. As another example, ethylene/vinyl chloride copolymers can be prepared by reductive elimination of chlorine from poly (vinyl chloride) (PVC). The driving force here is that, although ethylene and vinyl chloride can be copolymerised directly, the normal routes to these polymers give insufficient control over composition and sequence distribution. 

Poly (vinyl alcohol-co-vinyl acetate) polymers are surface active species which can be used to stabilise latex and oil in water dispersions. In order to understand the properties of these materials, it is necessary that their sequence distributions are well characterised. A number of NMR studies on the microstructure of PVA/PVAc copolymers have been made [51-53] (see also chapter 3). Moritani and Fujiwara [51], for example, have used proton and carbon-13 NMR spectroscopy to extract dyad distributions for a range of copolymers with different degrees of deacetylation. Samples were prepared using one of three routes direct saponification of PVAc alcoholyis of PVAc using sodium methoxide and reacetylation of PVA. From the polymer composition and the dyad distribution, the parameter rj was calculated for each polymer as follows ... 

Another method involves excimer fluorescence as a molecular probe see Section 2.9. The question may be raised as to whether polymer blends will become more miscible if the differences in their solubility parameters are reduced. Excimer fluorescence provides some evidence see Rgure 4.14 (52). Here, 0.2 wt.% of poly(2-vinyl naphthalene), P2VN, is dispersed in a series of poly (alkyl methacrylates). These include the following, which are identified in Figure 4.14 by acronym methyl, PMMA ethyl, PEMA n-propyl, PnPMA isopropyl, PiPMA n-butyl, PnBMA isobutyl, PiBMA . yec-butyl, PsBMA ferf-butyl, PtBMA phenyl, PPhMA, isobomyl, PiBoMA benzyl, PBzMA and cyclohexyl, PCMA. Two other host polymers were polystyrene, PS, and poly(vinyl acetate), PVAc. 

Parallel to C02-philic homopolymers and their upper critical solution density, the existence of both CMT and CMP transitions is actually indicative of a CMD. This concept was introduced by Buhler et al. [31], performing static and dynamic light-scattering studies on a poly(l,l-dihydroperfluorooctyl acrylate)-/>-poly(vinyl acetate) (PTAN-/>-PVAc) block copolymer (see Figure 13.22). The respective molecular weights of the blocks were 43,100 and 4400 g/mol. Through the examination of aggregation numbers this copolymer was found insoluble at densities lower... 

Method of synthesis because of Instability of vinyl alcohol, poly(vinyl alcohol) is produced by polymerization of vinyl acetate (see more in PVAc) and its subsequent hydrolysis ... 

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