Styrene repeat units

The distribution of styrene crosslinks in cured unsaturated polyesters based on maleic anhydride, phthalic anhydride, propylene glycol and dipropylene glycol is found to be dependent on the molar ratio of styrene vs. maleic/fumaric unit. If the molar ratio is higher than 1, the dyad distribution is predominant lower molar ratios yield mostly styrene microdomains, i.e. n-ads with more than 2 styrene repeating units 232>. 

Predict the ratio of butadiene to styrene repeating units initially produced by free radical copolymerization of an equimolar mixture of the two monomers at 50°C. (Use Table 6-5 below.)... 

The observation that Bib is more exothermic than Bz3 is not surprising when one considers the fact that blends of tetramethyl bisphenol-A polycarbonate with polystyrene are miscible while blends of bisphenol-A polycarbonate with polystyrene are immiscible (43 ). Apparently, substitution of methyl groups on the aromatic rings in the backbones of these materials enhances miscibility with the styrene repeat unit. The observation that Biz is also exothermic is quite surprising, considering the similarity of the trimethyl and dimethyl ether units. Using regular solution approximations, one could... 

Experimental. The sulfonated polystyrene (SPS) was obtained from Dr. Robert Lundberg of the Exxon Research and Engineering Company, and was prepared by procedures described elsetdiere[34]. The sample used in this study had 5.6 percent of the styrene repeat units sulfonated. The acid SPS was neutralized with 95% of the stoichiometric amount of nickel acetate in tetrahydrofuran/water solution, precipitated into water, then dried under vacuum at 120 C. 

Figure 6.1 FTIR spectra of (a) linear atactic polystyrene with molecular weight of 400 kDa, (b) poly(p-methylstyrene), and hypercrosslinked polystyrenes prepared by crosslinking styrene-0.5% DVB copolymer with (c) 0.3, (d) 0.5, (e) 1.0, and (0 1.5 mol of monochlorodimethyl ether per styrene repeating unit.

Figure 7.10 Dependence of weight swelling in toluene on the crosslinking degree of networks prepared by crosslinking linear polystyrene with (1) monochlorodimethyl ether and (2, 3) methylal in the presence of (1, 2) 1 and (3) 2 mol SnC per 1 mol of styrene repeating units. (After [53]).

Figure 7.44 Dependence of specific volume on temperature for hypercrosslinked networks prepared by post-crosslinking copolymers of styrene with (a) 0.17, (b) 0.6, and (c) 2.7% DVB by means of (1) 03, (2) 0.4, (3) 0.5, (4) 0.75, and (5) 1.0 mol of MCDE per styrene repeating unit. (Reprinted from [151] with permission of Wiley Sons, Inc.)...

On crosslinking, the molecular wei t of the polystyrene macromolecules of330 kDa should rise to 370 kDa for sample IHPS-18, due to the introduction of one additional —CH2- poup per styrene repeat unit (at the formal degree of crosshnking of the nanosponge of 200% attained). It could even amount to 390 kDa if the residual 6% chlorine is also taken into consideration. 

Positive interactions between cationic species, including protons, with aromatic structures comprise an intensively examined and already well-documented phenomenon [142, 143], In the hypercrosslinked polystyrene these interactions may well be enhanced by a possible presence of condensed aromatic systems. As was shown in Chapter 6, Section 4.4, anthracene-type structures may easily be formed by the condensation of two chloromethylated styrene repeating units, followed by a subsequent oxidation. However, the early elution of pure HCl in Fig. 12.1 does not imply any retentive interactions between protons and the polymer. The retention of HCl occurs only in the presence of a salt. But why would the properties of HCl in the polymeric phase change so dramatically in the presence of metal chlorides, while no association of HCl with LiCl or CaCl2 takes place in solution The version (i) of attractive interactions of protons with the polystyrene phase thus cannot be accepted without serious doubt. 

Macronet isoporous polymers with a degree of crosslinking less than 25% readily enter the reaction of chloromethylation. The amount of introduced chlorine, 20—22%, comes close to that corresponding to one CICH2 group per styrene repeating unit (23% Cl). 

DN values were computed using Gutmann s equation and the thermochemical data for binary polymer blends of a poly(styrene-co-vinylphenyl hexafluoro dimethyl carbinol) [55]. The copolymer contained 95% of styrene repeat units and its OH stretching frequency shifts were similar to those of HFIP [55]. For this reason the copolymer was assigned the Gutmann AN of HFIP [175]. 

One-photon (125 nm) and two-photon (193 nm) ionization mass spectra of 3 samples of polystyrene whose nominal Mp values are indicated in the figure. Some peaks are labeled with the number, n, of styrene repeat units. The low mass peak designated S in the 125-nm ionization spectra is styrene. Note the vertical scale change (x2) in these traces. 

The single most important characteristic of a polymer chain is the molar mass and it is important for the synthetic polymer chemist to be able to prepare polymer molecules with controlled size. The molar mass of the molecule in Figure 1(a) is 431 times the molar mass of a styrene repeat unit (104gmol ) plus the molar mass of the butyl (57 g mol ) and hydrogen (1 gmol ) end groups, that is, it is equal to 44882gmol While the... 

Numerous studies on poly(styrene sulfone) have shown that a copolymer containing an average of two styrene repeating units per sulfur dioxide unit could be prepared easily. Bovey and co-workers have shown that copolymers prepared near room temperature have a strong bias for a regular structure such as (I) (see Scheme 1). 

The role of sequence distribution on photochemical discoloration SAN has recently been reported. It was shown, using FT-IR, that chemkal changes occurring during photochemical degradation are a result of attack of the SAS triad sequences [77], Fiuther study revealed that the chemical attack was oamrring specifically at the styrene repeat units within the SAS tri [78]. 

Example 10.1 Starting with a batch reactor containing 1 x 10 moles of /j-BuLi in dilute solutions, suggest two methods for making the block copolymer [S]2oo—[B]iooo [S]20o. where [S] represents a styrene repeat unit and [B] represents a butadiene repeat unit. 

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