Poly blend forms

Conducting polymer blends based upon polyaniline (PANI) are a new class of materials in which the percolation threshold for the onset of electrical conductivity can be reduced to volume fractions well below that required for classical percolation (16% by volume for globular conducting objects dispersed in an insulating matrix in three dimensions) [277,278], The origin of this remarkably low threshold for the onset of electrical conductivity is the self-assembled network morphology of the PANI poly blends, which forms during the course of liquid-liquid phase separation [61],... 

MacKnight and coworkers found that several poly(imide)s, such as Ultem poly(ether imide) and XU218 poly(imide), formed miscible blends with poly (benzimidazole) (FBI) [58, 59]. The miscibility of these blends is believed to result from specific interactions between the benzimide ring of the poly(im-ide) and benzimidazole ring of FBI. In a later study, Grobelny et al. [60] reported the CFMAS spectra of several of these blends. Slight changes in the lineshape were observed in the intimate blends, and seen as evidence of the specific interactions between the polymers. In particular, the peak in the spectra, due to the imide carbonyl carbon, was seen to broaden towards... 

The ability of the EoS to predict the behavior of rubbery polymer solutions has been proved by various authorsI ° l. In this section we present two examples of the solubility of swelling penetrants in rubbery polymers, namely propane sorption in poly[dimethylsiloxane] (PDMS) at 35° C, and then toluene sorption in rubbery polymer blends formed by low-density poly [ethylene] (LDPE) and poly[vinylchloride] (PVC) at 30° C. 

Blends comprising sulfone polymers and other middle- to high-temperature engineering resins with at least a partially aromatic backbone structure are feasible in many cases. Such blends include sulfone polymer blends with polycarbonates, some polyesters, polyarylates, poly-etherimides, and polyaryletherketones. Blends of PPSF with poly-aryletherketones such as PEEK or PEK are particularly interesting as these blends form very finely dispersed systems with synergistic strength, impact, and environmental stress cracking resistance properties [43, 44]. 

In this study, binary blends formed by poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) were prepared by solution casting and evaluated by solution and solid-state NMR. Solid-state NMR was used to understand the behaviour of the ternary blends. 

Akiba I, et al. Nanostructured polymer blend formed from poly(N-vinylpyrrolidone) and end-fnnctional polystyrene. Polymer 2004 45(17) 5761-4. 

Sato A, Kato T, Uryu T (1996) Hydrogen-bonded liquid-crystaUine polymer blends formed from a thermotropic polyester containing a lateral pyridyl groups and poly(4-vinylphenol). J Polym Sci Polym Chem Ed 34 503-505... 

A large group of multi-phase polymeric systems is formed by the block copolymers, graft copolymers, random copolymers, and poly-blends. This group of polymers has received increasing attention (e.g. 27—29) because of the controllable, tailor-made properties of these engineering materials. Here the superstructure is determined by the relative weight, sequential order, and Hmited miscibihty or even incompatibility... 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

Polymer Applications. The reaction of sahcylaldehyde with poly(vinyl alcohol) to form an acetal has been used to provide dye receptor sites on poly(vinyl alcohol) fibers (89) and to improve the light stabihty of blend fibers from vinyl chloride resin and poly(vinyl alcohol) (90) (see Fibers, POLY(VINYL alcohol)). ... 

Adhesives. High concentration (>10%) solutions of poly(ethylene oxide) exhibit wet tack properties that are used in several adhesive appHcations. The tackiness disappears when the polymer dries and this property can be successfully utilized in appHcations that require adhesion only in moist conditions. PEO is also known to form solution complexes with several phenoHc and phenoxy resins. Solution blends of PEO and phenoxy resins are known to exhibit synergistic effects, leading to high adhesion strength on aluminum surfaces. Adhesive formulations are available from the manufacturers. 

Blends of poly(vinyl chloride) (PVC) and a-methylstyrene—acrylonitrile copolymers (a-MSAN) exhibit a miscibiUty window that stems from an LCST-type phase diagram. Figure 3 shows how the phase-separation temperature of 50% PVC blends varies with the AN content of the copolymer (96). This behavior can be described by an appropriate equation-of-state theory and interaction energy of the form given by equation 9. 

Copolymers of S-caprolactone and L-lactide are elastomeric when prepared from 25% S-caprolactone and 75% L-lactide, and rigid when prepared from 10% S-caprolactone and 90% L-lactide (47). Blends of poly-DL-lactide and polycaprolactone polymers are another way to achieve unique elastomeric properties. Copolymers of S-caprolactone and glycoHde have been evaluated in fiber form as potential absorbable sutures. Strong, flexible monofilaments have been produced which maintain 11—37% of initial tensile strength after two weeks in vivo (48). 

Poly(ethyl methacrylate) (PEMA) yields truly compatible blends with poly(vinyl acetate) up to 20% PEMA concentration (133). Synergistic improvement in material properties was observed. Poly(ethylene oxide) forms compatible homogeneous blends with poly(vinyl acetate) (134). The T of the blends and the crystaUizabiUty of the PEO depend on the composition. The miscibility window of poly(vinyl acetate) and its copolymers with alkyl acrylates can be broadened through the incorporation of acryUc acid as a third component (135). A description of compatible and incompatible blends of poly(vinyl acetate) and other copolymers has been compiled (136). Blends of poly(vinyl acetate) copolymers with urethanes can provide improved heat resistance to the product providing reduced creep rates in adhesives used for vinyl laminating (137). 

Because of the aqueous solubiUty of polyelectrolyte precursor polymers, another method of polymer blend formation is possible. The precursor polymer is co-dissolved with a water-soluble matrix polymer, and films of the blend are cast. With heating, the fully conjugated conducting polymer is generated to form the composite film. This technique has been used for poly(arylene vinylenes) with a variety of water-soluble matrix polymers, including polyacrjiamide, poly(ethylene oxide), polyvinylpyrroHdinone, methylceUulose, and hydroxypropylceUulose (139—141). These blends generally exhibit phase-separated morphologies. 

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