Styrene block polymers, physical

Figure 7. Physical properties of styrene-isoprene block polymers.

R.F. Storey, B.J. Chisholm, and M.A. Masse, Morphology and physical properties of poly(styrene-b-isobutylene-b-styrene) block copolymers, Polymer, 37(14) 2925-2938, July 1996. 

Sulfonation is very useful chemical modification of polymer, as it induces high polarity in the polymer changing its chemical as well as physical properties. Sulfonated polymers are also important precursors for ionomer formation [75]. There are reports of sulfonation of ethylene-propylene diene terpolymer (EPDM) [76, 77], polyarylene-ether-sulfone [78], polyaromatic ether ketone [79], polyether ether ketone (PEEK) [80], styrene-ethylene-butylene-styrene block copolymer, (SEBS) [81]. Poly [bis(3-methyl phenoxy) phosphozene] [82], Sulfonated polymers show a distinct peak at 1176 cm"1 due to stretching vibration of 0=S=0 in the -S03H group. Another peak appears at 881 cm 1 due to stretching vibration of S-OH bond. However, the position of different vibrational bands due to sulfonation depends on the nature of the cations as well as types of solvents [75, 76]. 

In the present study, the effects of composition, molecular weight, and heat treatment on the relaxation behavior of styrene—butadiene-styrene (SBS) block polymers are investigated. There is evidence (e.g., 6,7,8) that these types of multicomponent multiphase systems exhibit unusual phenomena in their dynamic mechanical behavior and in other physical properties. These are apparently related to the presence of the so-called interphase mixing region between the elastomeric and glassy domains. Similar evidence has been obtained by gas diffusion and sorption studies on the copolymer samples used in this investigation (9). 

In summary the hydrogenation of styrene-diene block polymers is a practical route to tough, clear heat-resistant plastics. Variations in overall physical properties can be obtained by controlling composition, microstructure, and the nature of the block sequence using conventional anionic polymerization techniques. 

The styrene-diene triblock copolymer consists of individual chains of three blocks, an elastomeric diene block in the center and a thermoplastic styrene block on each end. This polymer is called a thermoplastic elastomer. It exhibits some of the physical properties of elastomers at use temperature and is as pro-cessable as conventional plastics (5). The styrene/diene triblock copolymer has the unique morphology of glassy polystyrene domains in the rubbery diene matrix. Therefore, such an elastomer does not require conventional vulcanization since the glassy polystyrene domains act as physical crosslinks. 

This discovery culminated in the commercial production and the announcement (41) in 1965 of thermoplastic elastomers from block polymers of styrene and butadiene (S-B-S) and of styrene and isoprene (S-I-S). To rubber scientists and technologists the most outstanding property of S-B-S and S-I-S was the unvulcanized tensile strength compared to that of vulcanized NR and vulcanized SBR carbon black stocks. Stress-strain curves, to break, of these latter materials are compared to that of S-B-S in Figure 2. It was pointed out that the high strength of S-B-S must be due to physical crosslinks. 

Miyamoto, T., Kodama, K., and Shibayama, K. 1970. Structure and properties of a styrene-butadiene-styrene block copolymer. Journal of Polymer Science A-2 Polymer Physics 8 2095-2103. 

Mixtures of PPE and PS, or styrene-butadiene-styrene block copolymers have been extruded with maleic anhydride of fumaric acid to obtain compatibi-lized blends [42], In the same way, PPE with pendant glycidyl groups can be co-extruded with a poly(olefin) having anhydride groups [28], PPE can be grafted onto poly(ethylene) by melt kneading both modified polymers in the presence of a binder such as phenylenedi-amine. Both polymers are modified with maleic anhydride. The grafting takes place in situ. Amines may enhance the improvement of certain physical properties when used in combination with various compati-bilizers [29]. 

Block copolymers or graft copolymers made up of soft and rigid polymer sequences. Styrene block copolymers like polystyrene (PS) blocks [styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and styrene-ethylene-butylene-styrene (SEBS)], and polyester TPEs belong to this family. Structurally, the thermoplastic blocks form physical network knots within the polydiene. 

Lammertink, R.G.H., Hempenius, M.A., Thomas, E.L., and Vancso, G.J. (1999) Periodic organic-organometaUic microdomain structures in poly(styrene-block-ferrocenyldimethylsilane) copolymers and blends with corresponding homopolymers. Journal of Polymer Science Part B-Polymer Physics, 37,1009. 

H. Chen, D. F. Schmidt, M. Pitsikalis, N. Hadjichristidis, Y. Zhang, U. Wiesner, and E. P. Giannelis. Poly(styrene-block-isoprene) nanocomposites kinetics of intercalation and effects of copolymer on intercalation behaviors. Journal of Polymer Science, Part B Polymer Physics, 41 24 (2003), 3264-3271. 

Gradient copolymers can exhibit physical properties that are different than their block polymer analogues. Clough et al. describe experimental approaches based on fast and slow MAS NMR, which reveal the amount of rigid and soft phases in styrene-butadiene gradient copolymers with component specific resolution. The differences in structural mobility were shown by the different MAS techniques. ... 

The physical properties of the acid- and ion-containing polymers are quite interesting. The storage moduli vs. temperature behavior (Figure 8) was determined by dynamic mechanical thermal analysis (DMTA) for the PS-PIBMA diblock precursor, the polystyrene diblock ionomer and the poly(styrene)-b-poly(isobutyl methacrylate-co-methacrylic acid) diblock. The last two samples were obtained by the KC>2 hydrolysis approach. It is important to note that these three curves are offset for clarity, i.e. the modulus of the precursor is not necessarily higher than the ionomer. In particular, one should note the same Tg of the polystyrene block before and after ionomer formation, and the extension of the rubbery plateau past 200°C. In contrast, flow occurred in... 

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