The morphological development in blends of bisphenol-A polycarbonate (PC) and poly(methylmethacrylate) (PMMA) blends during isothermal annealing above 200 °C has been investigated where competition between liquid–liquid phase separation by spinodal decomposition and interchange reactions take place. Interchange reactions between PC and PMMA occurs at temperatures above 200 °C and leads to the formation of in situ graft copolymers from an ester–ester interchange reaction. During spinodal decomposition, graft copolymers are produced mainly at the interface region between the interconnected microphase domains. Instead of the usual ‘‘coarsening’’ process which is characteristic of the late-stage of spinodal decomposition, the mixture exhibits nearly monodisperse spherical domains as revealed by optical microscopy. This phenomenon is further studied through extensive small angle light scattering measurements. Resonance peaks up to fourth order are noted, a rare observation. The result clearly demonstrates that graft copolymers are formed in situ and can act as very effective ‘‘surfactants’’ in polymer blends. Furthermore, an attempt is made to analyze the angular dependence of the scattering intensity from this morphology with the Percus–Yevick hard sphere liquid theory. These results are believed to be general and therefore applicable to a wide variety of blends containing one or more components capable of an interchange reaction.
SYNOPSISA series of oxazoline-modified styrene-acrylonitrile (SAN) copolymers was prepared through the reaction of amino alcohols onto preformed SAN copolymers. Consequently, a variety of reactive copolymers were synthesized. The major focus of this study was to examine the influence of reaction conditions, i.e., the nature of the catalyst and amino alcohol structure, on reactivity. The ability to incorporate oxazoline groups onto preformed polymers is dependent on whether homogeneous reaction conditions are met. For example, the use of nonreactive solubilizing agents, i.e., cosolvent, is effective. However, optimum conditions are obtained when the INTRODUCTIONThe modification of the structure of polymeric materials has recently emerged as a n extremely active field in polymer science.'-5 An increasing variety of chemical reactions have been employed to produce polymers with novel and desirable physical and chemical properties. These reactions can be utilized to introduce functional, e.g., ion-containing polymers, and reactive groups, e.g., maleated polypropylene. This recent upsurge in interest in these types of polymers has been sparked in large part by their use as compatabilizers in blends.A majority of binary component blends are immiscible and therefore possess poor interfacial characteristics and poor mechanical properties. Blending is substantially enhanced with the addition of polymers of complementary functional groups such as in rubber-toughened blends containing groups that interact via coordination-type associations: In a similar manner, reactive processing * To whom correspondence should be addressed. Journal of Applied Polymer Science, Vol. 56,1673-1677 (1995 0 1995 John Wiley & Sons, Inc. CCC OOZl-S995/95/121673-05 techniques are used. For example, nylon 6 is rubbertoughened through the reaction with ethylene-propylene-diene terpolymer (EPDM) containing low amounts of maleic anhydride (EPDM-MA).7 Since nylon 6 contains one terminal amine group, its reaction with EPDM-MA produces a product that is a graft copolymer essentially free of crosslinking. These polymeric compatibilizers, whether formed through associations of complementary groups or chemical bonding between reactive functionalities, lower surface tension, promote interfacial adhesion, and substantially improve the size and distribution of the dispersed phase. Improved mechanical properties result. However, it is quite apparent that a large number of commercially available polymers cannot be easily and effectively utilized under reactive processing conditions. This report details the incorporation of relatively low levels of oxazoline functionality onto styreneacrylonitrile (SAN) copolymers. The synthetic procedure incorporates in a facile manner these reactive groups onto preformed SAN copolymers. As a result of this modification, a wide variety of reactive SAN copolymers can be produced spanning a range of acrylonitrile and oxazoline content. It is noteworthy 1673 1674 HSEIH, SCHULZ, AND PEIFFER that unfunctionalized SAN copolymers...
SYNOPSISThe chemical transformation of nitrile to oxazoline functionality via a soluble zinc saltcatalyzed reaction was conducted on a series of nitrile-containing copolymers, i.e., styreneacrylonitrile (SAN) and nitrile rubbers. The results show that triad tacticity of the acrylonitrile groups is important in understanding the relative reactivity of SAN copolymers. Furthermore, the dielectric properties of the comonomer is also a prime factor in understanding the different degrees of reactivity of SAN, nitrile rubbers, and its hydrogenated analog forms. Enhanced reaction rates are noted with higher dielectric constants. I NTRO DUCT10 NIt is well known that a majority of polymer blends require a compatibilizer in order to achieve a synergism in properties.'-' These compatibilizers are polymeric in nature, spanning the interfacial region between otherwise strongly phase-separated polymers. These compatibilizers are typically formed during melt processing, i.e., the blending step." This mode of formation is a solventless process and economic, and, in addition, the compatibility is formed in situ between the two phases. As a result of its location, the compatibility is immediately available to lower surface tension, promote interfacial adhesion, and lower the domain size of the dispersed phase. Markedly improved stress-strain properties result. Although this mode of blend formation is highly desirable, the procedure is limited to the number of commercially available polymers capable of being utilized under reactive processing conditions.Recently, a synthetic procedure was developed to incorporate low levels of oxazoline functionality onto styrene-acrylonitrile ( SAN) copolymers. It was noted that oxazoline groups are reactive toward a * To whom correspondence should be addressed. relatively wide range of functional groups. As a result, the utility of SAN copolymers as a blend compatibilizer should be substantially broader. In this report, we detail the oxazoline functionalization of a broad range of laboratory-synthesized and commercially available ( i.e., preformed) polymers containing nitrile groups. These families of materials include thermoplastics ( SAN copolymers) and rubbers ( nitrile rubbers, hydrogenated nitrile rubbers, and liquid rubbers). The former copolymers include styrene-nitrile copolymers which include random copolymers of SAN, alternating copolymers of SAN (alt-SAN) , and random copolymers of styrene-methacrylonitrile ( SMAN ) , while the latter systems include random copolymers of butadieneacrylonitrile ( NBR) and their hydrogenated analogs (HBNR). Therban 1701 possessed 34 wt % acrylonitrile and 100% of double bonds hydrogenated, and Therban 1701 SHRD possessed 34 wt % acrylonitrile and 96% of double bonds hydrogenated and were obtained from Mobay Chemicals. The reagents and solvents employed in this study were used as received (Aldrich Chemical). Zinc chloride was dried in a vacuum oven at 110°C for 2 days. 'H-NMR spectra were obtained from a 300 MHz Varian XL-300 instrument. EXPERIMENTAL
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