Properties of random and block copolymers of butadiene and styrene. I. Dynamic properties and glassy transition temperatures

Abstract

synopsisThe effect of monomer sequence on physical properties was investigated for butadienestyrene solution copolymers made by organolithium initiation. The polymers varied from random copolymers of uniform composition along the polymer chain to ideal block polymers of specific block sequence arrangement and included rubbers of intermediate degrees of randomness. Uniform composition random copolymers exhibit a single glaw transition temperature and a very narrow dynamic loss peak corresponding to this transition. The glass transition can be predicted from the styrene content and the microstructure of the butadiene portion of the rubber. Random copolymers in which compe sition varies along the polymer chain, and to some extent between molecules, exhibit a single glass transition, but the dynamic loss peak is broadened. The extent of this broadening is shown to be compatible with the sequence distribution, polymer segments of various compositions losing mobility a t different temperatures. This indicates a tendency for association between segments of different temperatures. This indicates a tendency for association between segments of different chains which are similar in composition. Block copolymers display two transitions, corresponding to T, for each type of block. The position and width of the dynamic loss peaks are related to block length and compositional purity of the blocks. 1581

Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations

“…A major driver of interest in such systems is that, by adjusting the length of the tapered region, one can tune microphase behavior and physical properties such as glass transition temperature (T g ) and orderdisorder transition temperature (T ODT ), as has been found in experiments by multiple groups. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] As would be intuitively expected, adding a taper generally increases the miscibility of the system, effectively decreasing the segregation strength (quantified by χN, the Flory χ parameter times polymer length) and widens the interfacial regions of the microphase separated structures. Furthermore, tapering has been shown to change the microphase behavior and dynamics versus typical diblocks in ways that cannot be explained by a simple shift in effective segregation strength.…”

Morphology and mechanical properties of styrene-butadiene-styrene/poly(methyl methacrylate-co-n-butyl acrylate) interpenetrating polymer networks

“…The unique microstructure, composed of two separate phases of hard plastic-like segments and soft elastomeric segments, of styrenic block copolymers was studied by many researchers [23][24][25][26] as well as the effect of solvent on their microstructures [27][28][29]. Nevertheless, the data for the morphology of styrenic block copolymers used as a component of IPNs can hardly be found.…”

Dynamics and thermodynamics of the liquid state (T < Tg) of amorphous polymers

“…8). A computer-drawn linear regression line (not shown) through these data points gives The T line is from Shen et al [146] but an equilibrium value of T was calculated by the method of Kraus et al [145] for a PBD of the same microstructure. TPP from diblocks probably high because of immobile PS end block.…”

“…The points for 38,000 molecular weight a r e on branch B-D of The vinyl contents are essentially the same but the trans/cis ratio is estimated at 3:l compared to 1 : l for the data of Sidorovitch et al Isomer content for the butadiene in SBR was estimated by us from plots of cis, trans, and vinyl a s a function of polymerization temperature, a s presented by Wood [144]. Kraus et al [145] give T g for amorphous c i s and trans PBD's as -114 and -102"C, compared to -7°C for vinyl. This means that T (and hence presumably Tan) is not too much affected by the cis-trans ratio as compared with a very large dependence on vinyl content.…”

“…21 o r from Eqs. (10) eAn estimate of Tg for the 40/40/20 cis/trans/vinyl PBD of P erences cited.based on curves in[141].and (11).Sidorovitch et al "74 using the method of Kraus et al[145] gives T = 186°K. g original papers) and TpQ calculated by our regression program.…”