Polystyrenes precursor

The synthesis of comb-like polymers with regular branching (in contrast to random branching) has been performed in the following way 91) A linear polystyrene precursor fitted with carbanionic sites at both ends is reacted first with 1,1-diphenylethylene (to decrease the nucleophilicity of the sites) and then with a calculated amount of triallyloxytriazine to get chain extension. Each triazine residue still carries one allyloxy... 

Polystyrene-polyamide block copolymer synthesis 63> also involves some kind of site transformation. The polystyrene precursor is fitted at chain end with a function... 

Studies on the dilute solution behavior of sulfonated ionomers have shown these polymers to exhibit unusual viscosity behavior in solvents of low polarity. These results have been interpreted as arising from strong ion pair associations in low polarity diluents. Solvents of higher polarity, such as dimethyl sulfoxide and dimethyl formamide induce classic polyelectrolyte behavior in sulfonate ionomers even at very low sulfonate levels. To a first approximation these two behaviors, ion pair interactions or polyelectrolyte behavior, are a consequence of solvent polarity. Intramolecular association of Lightly Sulfonated Polystyrene (S-PS) results in a reduced viscosity for the ionomer less than that of polystyrene precursor at low polymer levels. Inter-association enhances the reduced viscosity of the ionomer at higher polymer concentrations. Isolation of the intra- and inter-associated species of S-PS has been attempted (via freeze drying). A comparison of selected properties reveals significant differences for these two conformations. 

If the network is ideal, all hnear chains of the polystyrene precursor have been converted into a network of elastically active chains and, therefore, their number u is... 

Figure 1.6 Theoretical variation of swelling Q vs. functionality f molecular weight of polystyrene-precursor is (1) 80,000 (2) 20,000, and (3) 10,000 Da. (Reprinted from [125] with kind permission of American Chemical Society).

Figure 1.13 Calculated relation between molecular weight of polystyrene precursor, M, and swelling in benzene of model networks, assuming = = 0.354v and...

The distance between neighboring junctions in a dry network, calculated from neutron scattering by Benoit and coauthors [135] increases with the molecular weight of the polystyrene precursor (Table 1.4). This distance increases also on sweUing of the network in good solvents. At that, the product of d and was found to remain constant (at least, up to the very high sweUing of about 10). This relation points to the affinity of network deformation, that is, to the expected proportionaHty between the network volume and the distance between its junction points. 

Figure 1.14 Plot of swelling ys. temperature for two model networks based on polystyrene precursor with molecular weight of (1) 31,500 and (2) 14,700 Da. (After[143]).

The intramolecularly hypercrossfinked and toluene-passivated polystyrene material can be precipitated firom the synthesis solution with methanol in the form of a fine, slightly yellow powder. The latter remains soluble in dichloroethane, toluene, chloroform, and dioxane, that is, in the thermodynamically good solvents for the polystyrene precursor, and the solutions remain clear and stable for a long period. 

Figure 8. Typical GPC traces of SGLC-coil BCPs via polymer analogous reaction [62] (see Scheme 9 for structures) (a) polystyrene precursor (b) styrene -isoprene diblock copolymer (c) hydroxylated styrene-isoprene diblock copolymer (unimolecular micelle in tetrahydrofuran) (d) final FLC-coil diblock copolymer.

After these initial considerations, the complete analysis of a number of diblock copolymers of styrene and methyl methacrylate shall be discussed in detail. The poly(styrene-ftlodc-methyl methacrylate)s under investigation were prepared via anionic polymerization of styrene and subsequent polymerization of methyl methacrylate, varying molar mass and composition (B1-B3). The polystyrene precursors (P1-P3) were isolated and characterized separately. As the PMMA block is the more polar block in the block copolymer, a polar (silica gel) column was chosen for establishing the critical point of PMMA. According to case (1) in Fig. 14, the PS block is then eluted in the SEC mode. The behavior of PMMA of different molar masses on silica gel Si-100 in eluents comprising methylethylketone and cyclohexane is shown in Fig. 15A [37]. 

Estimated from the data of the diblock copolymer and polystyren precursor. "Determined from infrared spectra. 

Estimated from of polystyrene precursor and composition of P4VP blocks. 

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