Poly 2,6-dimethyl-l,4-phenylene oxide PPO

Also the polymorphic behavior of s-PS can be altered by blending, in particular with poly-2,6-dimethyl-l,4-phenylene oxide (PPO), both for the case of crystallization from the melt [104] and for the case of crystallization from the quenched amorphous phase [105]. 

The chemical modification of poly (2,6-dimethyl-l,4-phenylene oxide) (PPO) by several polymer analogous reactions is presented. The chemical modification was accomplished by the electrophilic substitution reactions such as bromination, sulfonylation and acylation. The permeability to gases of the PPO and of the resulting modified polymers is discussed. Very good permeation properties to gases, better than for PPO were obtained for the modified structures. The thermal behavior of the substituted polymers resembled more or less the properties of the parent polymer while their solution behavior exhibited considerable differences. 

In order to determine the necessity and/or the length of the spacer that is required to achieve liquid crystalline behavior from flexible vs. rigid polymers, we have introduced mesogenic units to the backbones of a rigid [poly(2,6-dimethyl-l,4-phenylene oxide) (PPO)] and a flexible [poly(epichlorohydrin) (PECH)] polymer through spacers of from 0 to 10 methylene groups via polymer analogous reactions. 

Gebreyes K, Frisch HL (1988) Improved synthesis and characterization of interpenetrating polymer networks of poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) and poly(dimethylsiloxane) (PDMS). J Poly Sci Part A Poly Chem 26(12) 3391-3395... 

Poly(2,6-dimethyl-l,4-phenylene oxide) (PPO).— The photo-oxidation of this polymer has attracted some interest. Wandelt has found that the photoinitiated oxidation of PPO depends upon the mobility of one more unit in the polymer chain. A marked increase in the rate of photo-oxidation of the polymer occurs in the temperature range 45—60 °C, which corresponds with the j -relaxation phenomena. Chain mobility markedly controls the diffusion of oxygen. From detailed analysis of the products of PPO photo-oxidation the following reaction schemes have been proposed to account for hydroperoxide photolysis (Scheme 22) and quinone photoreaction with aromatic aldehydes to give aromatic esters, for example (16) (Scheme 23). The three chromophores are formed during... 

The miscibility of different Cgo-containing polystyrenes with other polymers was studied in attempts to transfer the fullerene properties to the resulting polymer blends [71]. It was found that poly(2,6-dimethyl-l,4-phenylene oxide), PPO, is miscible with all the PS/Cgo samples investigated, whereas in the case of poly (vinyl methyl ether), PVME, PS/Cgo samples were miscible only for lower contents of Cgo [71]. 

This paper reports what we believe to be the first true IPN, i.e., no grafting between polymers and a single phase morphology (i.e., complete chain entanglement). In order to achieve this, pol3nners of known compatibility were used. Thus, IPN s, pseudo-IPN s (PDIPN s - only one polymer crosslinked), and linear blends of polystyrene (PS), and poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) (whose compatibility has been reviewed elsewhere (14)) were prepared by the simultaneous interpenetrating network (SIN) technique. The polystyrene was crosslinked by incorporating divinylbenzene. Several methods have been reported to synthesize... 

Schauer et al. (2003) used poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) membranes to separate water-EtOH mixtures by PV. Asymmetric membranes were prepared from solutions containing chloroform as a solvent and 1-butanol as a nonsolvent via the phase inversion technique. Dense membranes were prepared from chloroform solution by evaporation. Nonporous membranes (membranes precipitated from solutions with a small amount of the nonsolvent or prepared by evaporation) were preferentially permeable to water. Microporous membranes (prepared from solutions with a large amount of the nonsolvent) were preferentially permeable to EtOH, provided the membrane was not wetted by the feed solution. 

The majority of dynamic-mechanical studies for poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) provide evidence for only a weak shoulder (y relaxation) in the vicinity of 125-160 K however, a distinct peak has been observed by dielectric measurements [66,67]. In addition, there is evidence for a broad, low-intensity /8 peak in the range from 240 to 370 K. Sample preparation and impurities appear to have a significant effect on the appearance of the... 

Polymers, such as poly(N-vinyl-2-pyrrolidone) (PVP), polyacrylamide (PAA), modified poly(2,6-dimethyl-l,4-phenylene oxide) (PPO), and polysulfone (PSF) are used to prepare polymer-supported palladium catalysts. As the data summarized in Table 5, the polymer-supported Pd catalysts are very active in the carbonylation of allylbromide. They are much more active and efficient than the homogeneous palladium catalyst, PdCl2(P(C6H5)s)2. The higher activity of the polymer-supported palladium catalyst possibly results from the increased... 

For example, polystyrene homopolymer is brittle, and under impact loading it tends to crack. Fligh-impact polystyrene, HiPS, the graft copolymer of polystyrene with 5% to 10% polybutadiene, crazes first. A blend of this graft copolymer with poly(2,6-dimethyl-l,4-phenylene oxide), PPO, undergoes shear yielding first, then crazes. The ABS plastics craze, but with some shear yielding. 

Many miscible blends with single TgS are commercially available [6], the most interesting being Noryl 731 (General Electric Co.), which is a blend of polystyrene (PS) and poly(2,6-dimethyl-l,4-phenylene oxide) (PPO, 50% by weight). 

The miscibility of some polymer blends is of considerable technological importance although, fundamentally, the reasons for the miscibility are not completely understood. Polystyrene (PS) and poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) is one such system. 2D correlation studies have been made on a blend of 80% of the former and 20% of the latter by Palmer et al. [31]. The results suggest a different dynamic behaviour for the PS and PPO portions of the blend, depsite their compatibility, with the PS chains responding to the perturbing force faster than those of PPO. Some asynchronous cross peaks develop between the constituents, indicating the possible existence of submolecular level microheterogeneity. 

The effects of molecular orientation on the crystallization and polymorphic behavior of SPS and SPS/poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) blends were studied with wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry [37]. The oriented amorphous films of SPS and SPS/ PPO blends were crystallized under constraint at crystallization temperatures ranging from 140 to 240 °C. The degree of crystallinity was lower in the cold-crystallized oriented film than in the cold-crystallized isotropic film. It was inferred that the oriented mesophase was obtained in drawn films of SPS and that the crystallization of SPS was suppressed in that phase. The WAXD measurements showed that the crystal phase was more ordered in SPS/PPO blend than in pure SPS under the same annealing conditions. It was principally due to the decrease in the mesophase content. The crystal forms were found to be dependent on the crystallization temperature, blend composition, and... 

Zhang, S., Wu, C., Xu, T., Gong, M., Xu, X. (2005) Synthesis and characterizations of anion exchange organic-inorganic hybrid materials based on poly(2,6-dimethyl-l,4-phenylene oxide) (PPO). Journal of Solid State Chemistry, 178, 2292-2300. 

In recent years the structure and local composition of polymer blends has attracted much attention due to the commercial importance of these materials. The question of compatibility of the components is always paramount and Wetton et showed that dielectric studies provided information which was difficult to obtain by any other method. Random copolymers of styrene and 4-chlorostyrene were blended with poly(2,6-dimethyl-l,4-phenylene oxide) (PPO). It was shown that compatible blends containing 60% (w/w) of copolymer gave an a relaxation which was far broader than those observed for the parent polymer and copolymer, being indicative of microphase separation in the blend where the domains are smaller than the wavelength of light. This loss-peak-broadening is of the kind observed for mixtures of dibutylphthalate and o-terphenyl where microseparation of the components was inferred, and shows that dielectric studies can demonstrate such incompatibility on the microscale in materials which appear to be compatible when judged by optical or DSC measurements. 

Poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) is most frequently synthesized by the oxidative polymerization of 2,6-dimethylphenol which should result in a polymer containing one phenyl and one phenolic chain end (PPO-OH) (see also Chapter 28 of Volume 5). However, in all cases, a disproportionation reaction occurs to form the side product 3,3, 5,5 -tetramethyl-4,4 -diphenylquinone, which reacts with PPO-OH according to equation (65) in Scheme 62 to yield a certain amount of PPO containing two phenol chain ends (PP0-20H). More recently, Heitz and co-workers and Nava and Percec have developed procedures to prepare PP0-20H according to equations (64) and (66) in Scheme 62. 

The Gomez-Ribelles theoretical approach has been used to reproduce the enthalpy relaxation of several blends of PS/poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) [70], Results show that the distribution of relaxation times is broader in the blends than in the individual components. In terms of the Angell [71] concept of fragile-strong classification of materials, the blends were stronger than the component parts. 

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