Polymer blends with polyisoprene

How much of a crystallizable material X can I blend uniformly into a polymer until it starts to form crystals A series of blends with increasing amount of X is prepared. The samples are studied by WAXS (cf. Sect. 8.2) using laboratory equipment. Crystalline reflections of X are observed, as X starts to crystallize. Peak areas can be plotted vs. the known concentration in order to determine the saturation limit. Think of X being Ibuprofen and Y a polystyrene-(7 )-polyisoprene copolymer, and you have an anti-rheumatism plaster. 

Recent studies of blends of polyisoprene (PIP) with polybutadiene (PBD) have revealed a number of remarkable features [1-5]. Non-polar hydrocarbon polymers such as PIP and PBD are not expected to exhibit miscibility given the absence of specific interactions. When the polybutadiene is high in 1,2 microstructure, however, it has a remarkable degree of miscibility with PIP. This miscibility is the consequence of a close similarity in both the polarizability and the expansivity of the two polymers [3,4]. Their mixtures represent a very unusual instance of miscibility between chemically distinct, non-reacting homopolymers. As its 1,4- content increases, both the polarizability and the thermal expansivity of the PBD diverge from that of PIP, resulting in a reduced degree of miscibility. This effect of PBD microstructure on miscibility with PIP can be seen in the data in Table I [3]. ... 

Polybutadiene, CAS 9003-17-2, is a common synthetic polymer with the formula (-CH2CH=CHCH2-)n- The cis form (CAS 40022-03-5) of the polymer can be obtained by coordination or anionic polymerization. It is used mainly in tires blended with natural rubber and synthetic copolymers. The trans form is less common. 1,4-Polyisoprene in cis form, CAS 9003-31-0, is commonly found in large quantities as natural rubber, but also can be obtained synthetically, for example, using the coordination or anionic polymerization of 2-methyl-1,3-butadiene. Stereoregular synthetic cis-polyisoprene has properties practically identical to natural rubber, but this material is not highly competitive in price with natural rubber, and its industrial production is lower than that of other unsaturated polyhydrocarbons. Synthetic frans-polyisoprene, CAS 104389-31-3, also is known. Pyrolysis and the thermal decomposition of these polymers has been studied frequently [1-18]. Some reports on thermal decomposition products of polybutadiene and polyisoprene reported in literature are summarized in Table 7.1.1 [19]. 

Eisenberg and coworkers have employed acid-base interactions to improve the miscibility of a number of polymer-polymer pairs. Miscible blends were prepared using acid-base interactions, e.g., with SPS (acid derivative) and poly (ethylacrylate-co-4-vinylpyrldine) (91), sulfonated polyisoprene and poly (styrene-co-4-vinylpyridine) (92), and using ion-dipole interactions, e.g., poly (styrene-co-llthium methacrylate) and poly (ethylene oxide) (93). Similarly, Weiss et al. (94) prepared miscible blends of SPS(acid) and amino-terminated poly (alkylene oxide). In addition to miscibility improvements, the interactions between two functionalized polymers offers the possibility for achieving unique molecular architecture with a polymer blend. Sen and Weiss describe the preparation of graft-copolymers by transition metal complexation of two functionalized polymers in another chapter. 

While earlier attempts to produce satisfactory synthetic rubber from iso-prene were unsuccessful, in 1955 American chemist Samuel Emmett Horne Jr. (b. 1924) prepared 98 percent czr-l,4-polyisoprene via the stereospecific polymerization of isoprene. Home s product differs from natural mbber only in that it contains a small amount of rfr-l,2-polyisoprene, but it is indistinguishable from natural mbber in physical properties. First produced in 1961, BR (for butadiene mbber), a mbberlike polymer that is almost ex-clnsively czr-1,4-polybutadiene, when blended with natural or SBR mbber, has been nsed for tire treads. 

The polymer industry traces its beginning to the early modifications of shellac, natural rubber (NR — an amorphous c -l,4-polyisoprene), gutta-percha (GP — a semi-crystalline trfl i-l,4-polyisoprene), and cellulose. In 1846, Parkes patented the first polymer blend NR with GP partially co-dissolved in CSj. Blending these two isomers resulted in partially crosslinked (co-vulcanized) materials whose rigidity was controllable by composition. The blends had many apphcations ranging from picture frames, table-ware, ear-trumpets, to sheathing the first submarine cables. 

Bhowmick et al. [1986] investigated properties of cis- and trans-polyisoprene blends (cPI/tPI), with a rather cursory look at the effect of gamma irradiation (Table 11.9). The blends consisted of guayule mbber (cPI) and synthetic tPI (Trans-PIP from Polysar). The blends were prepared by mixing the two polymers, along with the typical... 

The study of electroconductive polymer systems, based on conductive particles and polymer blends, has been quite intensive during the recent past. Gubbels et al. [149] studied the selective localization of CB particles in multiphase polymeric materials (PS and PE). According to these results, the percolation threshold may be reduced by the selective localization of CB. The minimum resistivity was obtained when double percolation (phase and particle percolation) exists in the PS-PE blend. In addition, it was found that the percolation threshold may be obtained at very low particle concentrations, provided that CB is selectively localized at the interface of the blend components. Soares et al. [150] found that the type of CB (i.e., different surface areas) does not affect the conductivity of the blend with 45/55 PS/PIP (polyisoprene) composition. 

Dielectric loss e" measured at 10°C for a PI12/PVE60 miscible blend with Mp = 1.2 x W, Mpvp = 6 X lO, and Wp, = 17 wt% (circles). Dotted and solid curves, respectively, indicate the results of fitting with Havriliak-Negami empirical equation without and with the mode broadening due to the concentration fluctuation. (Data taken, with permission, from Hirose, Y., O. Urakawa, and K. Adachi. 2004. Dynamics in disordered block copolymers and miscible blends composed of poly(vinyl ethylene) and polyisoprene. /. Polym. Sci. Part B Polym. Phys. 42 4084-4094.)... 

Test of time-temperature superposabillty for the dielectric P data of low-M and middle-M poly-isoprene/poly(p-feri butyl styrene) (PI/PtBS) miscible blends as indicated. In panels (a)-(d), the sample code numbers of the blends denote Kh M of the components. The reference temperature is T, = 90°C for aU blends. The solid curves indicate the e" data of bulk PI corrected for the PI volume fraction in the blends. These curves are shifted along the axis to match their peak frequency with that of the blends. (Etata taken, with permission, from Chen, Q., Y. Matsumiya, Y. Masubuchi, H. Watanabe, and T. Inoue. 2008. Component dynamics in polyisoprene/ poly(4-tert-butylstyrene) miscible blends. MacrvmoJeades 41 8694-8711 Chen, Q., Y. Matsumiya, Y. Masubuchi, H. Watanabe, and T. Inoue. 2011. Dynamics of polyisoprene-poly(p-tert-butylstyrene) diblock copolymer in disordered state. Macnmiolecules 44 1585-1602 Chen, Q., Y. Matsumiya, K. Hiramoto, and H. Watanabe. 2012. Dynamics in miscible blends of polyisoprene and poly(p-terf-butyl styrene) Thermo-rheological behavior of components. Polymer ]. 44102-114.)... 

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