Poly solubihty

A solubihty parameter of 24.5-24.7 MPa / [12.0-12.1 (cal/cm ) ] has been calculated for PVF using room temperature swelling data (69). The polymer lost solvent to evaporation more rapidly than free solvent alone when exposed to air. This was ascribed to reestabUshment of favorable dipole—dipole interactions within the polymer. Infrared spectral shifts for poly(methyl methacrylate) in PVF have been interpreted as evidence of favorable acid—base interactions involving the H from CHF units (70). This is consistent with the greater absorption of pyridine than methyl acetate despite a closer solubihty parameter match with methyl acetate. 

Polymer—polymer iacompatibiHty encapsulation processes can be carried out ia aqueous or nonaqueous media, but thus far have primarily been carried out ia organic media. Core materials encapsulated tend to be polar soHds with a finite degree of water solubiHty. EthylceUulose historically has been the sheU material used. Biodegradable sheU materials such as poly(D,L-lactide) and lactide—glycoHde copolymers have received much attention. In these latter cases, the object has been to produce biodegradable capsules that carry proteias or polypeptides. Such capsules tend to be below 100 p.m ia diameter and are for oral or parenteral administration (9). 

Significant use properties of poly(ethylene oxide) are complete water solubiHty, low toxicity, unique solution rheology, complexation with organic acids, low ash content, and thermoplasticity. 

SolubiHty parameters of 19.3, 16.2, and 16.2 (f /cm ) (7.9 (cal/cm ) ) have been determined for polyoxetane, po1y(3,3-dimethyl oxetane), and poly(3,3-diethyloxetane), respectively, by measuring solution viscosities (302). Heat capacities have been determined for POX and compared to those of other polyethers and polyethylene (303,304). The thermal decomposition behavior of poly[3,3-bis(ethoxymethyl)oxetane] has been examined (305). 

Poly(vinyl alcohol) used to manufacture the poly(vinyl acetal)s is made from poly(vinyl acetate) homopolymer (see Vinyl polymers, vinyl alcohol polymers Vinyl POLYMERS, vinyl acetate polymers). Hydrolysis of poly(vinyl acetate) homopolymer produces a polyol with predominandy 1,3-glycol units. The polyol also contains up to 2 wt % 1,2-glycol units that come from head-to-head bonding during the polymeri2ation of vinyl acetate monomer. Poly(vinyl acetate) hydrolysis is seldom complete, and for some appHcations, not desired. For example, commercial PVF resins may contain up to 13 wt % unhydroly2ed poly(vinyl acetate). Residual vinyl acetate units on the polymer help improve resin solubiHty and processibiHty (15). On the other hand, the poly(vinyl alcohol) preferred for commercial PVB resins has less than 3 wt % residual poly(vinyl acetate) units on the polymer chain. 

The solubihty of representative poly(vinyl formal) resins is as follows in single solvents, where S = soluble and I = insoluble ... 

Drying of the poly(vinyl alcohol) is critical to both the color and solubiHty of the final product. Excessive drying temperatures result in high product color and an increase in the crystallinity, which in turn reduces the solubiHty of the product. Drying is initially subjected to a flash regime, where the solvent not contained within the particles is flashed off. This first phase is foUowed by a period where the rate is controUed by the diffusion rate of solvent from the poly(vinyl alcohol) particles. Because the diffusion rate falls as the material dries, complete drying is not practical. The polymer is therefore generally sold at a specification of 95% soHds. 

Maleimides Alkyl and aryl maleimides in small concentrations, e.g., 5-10 wt% significantly enhance yield of cross-link for y-irradiated (in vacuo) NR, cw-l,4-polyisoprene, poly(styrene-co-butadiene) rubber, and polychloroprene rubber. A-phenyhnaleimide and m-phenylene dimaleimide have been found to be most effective. The solubihty of the maleimides in the polymer matrix, reactivity of the double bond and the influence of substituent groups also affect the cross-fink promoting ability of these promoters [82]. The mechanism for the cross-link promotion of maleimides is considered to be the copolymerization of the rubber via its unsaturations with the maleimide molecules initiated by radicals and, in particular, by allyfic radicals produced during the radiolysis of the elastomer. Maleimides have also been found to increase the rate of cross-linking in saturated polymers like PE and poly vinylacetate [33]. 

In most cases the catalytically active metal complex moiety is attached to a polymer carrying tertiary phosphine units. Such phosphinated polymers can be prepared from well-known water soluble polymers such as poly(ethyleneimine), poly(acryhc acid) [90,91] or polyethers [92] (see also Chapter 2). The solubility of these catalysts is often pH-dependent [90,91,93] so they can be separated from the reaction mixture by proper manipulation of the pH. Some polymers, such as the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers, have inverse temperature dependent solubihty in water and retain this property after functionahzation with PPh2 and subsequent complexation with rhodium(I). The effect of temperature was demonstrated in the hydrogenation of aqueous allyl alcohol, which proceeded rapidly at 0 °C but stopped completely at 40 °C at which temperature the catalyst precipitated hydrogenation resumed by coohng the solution to 0 °C [92]. Such smart catalysts may have special value in regulating the rate of strongly exothermic catalytic reactions. 

An interesting family of polymeric ligands show inverse temperature dependence of solubihty in water, i.e. they can be precipitated from aqueous solutions by increasing the temperature above the so-called cloud point. Typically these ligands contain poly(oxyalkylene) chains, but the phenomenon can be similarly observed with poly(N-isopropyl acrylamide) derivatives (e.g. 132) and methylated cyclodextrins, too. At or above their cloud points these compounds fall off the solution, due to the break-up and loss of the hydration shell which prevents aggregation and precipitation of their molecules. Conversely, upon cooling below this temperature (also called the lower critical solution temperature, LCST) these substances dissolve again. 

Table 1 summarizes the values of ki and ki2 determined in salt-free and sahne water containing 0.1 M KCl, together with the solubihties of the poly-... 

Silicone Resins. Silicone resins ate an unusual class of oiganosiloxane polymers. Unlike hneat poly(siloxanes), the typical sihcone resin has a highly branched molecular stmcture. The most unique, and perhaps most usefvil, characteristics of these materials ate their soluhflity in oiganic solvents and apparent miscibility in other polymers, including sflicones. The incongruity between solubihty and three-dimensional stmcmre is caused hy low molecular weight < 10, 000 g/mol) and broad polydispersivity of most sihcone resins. 

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaHties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiHty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiHty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

In an attempt to increase Tg of the poly[bis(o-carboxyphenoxy)alkanes], Anastasiou and Uhrich (2000a) replaced the alkane moiety by ortho-, meta-, and para-xylenes producing poly[a-/m-bis(p-carboxyphenoxy)xylene]s (Pa-p-CPX, and Pm-p-CPX) and poly[o-/m-/p-bis(o-carboxyphenoxy)xylene]s (Pa-a-CPX, Pm-a-CPX, and Pp-a-CPX). They found Pa-p-CPX to be relatively insoluble and were unable to synthesize poly p-bis(p-carboxy-phenoxy)xylene] because of the insolubility of the dicarboxylic acid (Anastasiou and Uhrich, 2000a). Pa-a-CPX and Pm-a-CPX demonstrated the most favorable solubihty and neither exhibited a melting temperature. All of the polymers synthesized had TgS between 71 and 101°C (Anastasiou and Uhrich, 2000a). 

KUC Kuckling, D., Adler, H.-J.P., Arndt, K.F., Ling, L., and Habicher, W.D., Temperature and pH dependent solubihty of novel poly(A-isopropylacrylamide) copolymers,Macrowzo/. Chem. Phys., 201, 273, 2000. 

By definition, ionomers are copolymers with a few molar percent ionic groups inserted on their chain backbones. The solubihty of ionomers in water mainly depends on the chemical nature of the chain backbone. For example, polystyrene ionomers are insoluble in water and poly(acrylamide) ionomers are completely soluble in water in the temperature range 0-100 °C. Water-insoluble ionomers have been extensively studied and reviewed and these reviews can be easily found in the literature. Hereafter we will discuss only ionomers soluble in water. 

Polymeric micelles Poly(ethylene glycol)-polyOactide) Cyclosporin A Solubihty enhancement of poorly soluble cyclosporin A and furdier improving oral absorption of the drug [117]... 

LE1 Lee, S.-H., LoStracco, M.A., Hasch, B.M., and McHugh, M.A., Solubihty of poly(ethylene-co-aciyhc acid) in low molecular weight Itydrocaibons, J. Phys. Chem., 98,4055,1994. 

Lin H, Freeman BD. Gas solubihty, diffusivity and permeability in poly(ethylene oxide). J Membr Sci 2004 239 105-117. 

Temperature-responsive behavior was also observed for gels formed by worm-like micelles of poly(styrene)-bZocA -poly(iV-isopropyl acrylamide). Poly(iV-isopro-pyl acrylamide) molecules are known to associate when the ambient temperature is increased above their lower critical solubihty temperature (LCST) of 32 °C [215]. When the gel was heated to a temperature above the LCST of the poly(A-isopropyl acrylamide) block, a nanofibrillar network was formed [167, 177]. The association of poly(A-isopropyl acrylamide) was reversible [215] cooling of the nanofibrillar gel led to dissociation of the polymer network. 

Several industries including the aerospace industry use rapid prototyping. Prototypic materials use polyethylene glycol having molecular weight of 600 daltons as plasticizer for poly(2-ethyl-2-oxaline), PEO, a polymer used for making prototypes. Plasticizer enhances overall water solubihty of PEO and its dissolution rate." ... 

However, the influence of polar comonomer units on polymer solubihty is in general neither Hnear nor necessarily monotonic. Fig. 2.6a shows the ethylene solubility of poly(ethylene-co-methyl acrylate) copolymers for different amounts of the methyl acrylate monomer in the copolymer from 0 mol% (corresponds to LDPE) to 44 mol%. For small amounts of the methyl acrylate monomer, favorable interactions of the methyl acrylate units of the copolymer with the quadru-pole moment of the ethylene enhance the solubility of the copolymer. Here, the copolymers first show a decreasing cloud point pressure. However, upon further increase of the methyl acrylate contents (above 13 mol%), the importance of the polar intermolecular interactions between the different methyl acrylate units of the copolymer molecules becomes dominant, leading to decreasing solubility. However, for the similar system poly(ethylene-co-propyl acrylate), very different behavior is observed. Here, the solubility of the copolymer increases with in-... 

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