Swelling solvent

The in situ bulk polymerization of vinyl monomers in PET and the graft polymerization of vinyl monomers to PET are potential useful tools for the chemical modification of this polymer. The distinction between in situ polymerization and graft polymerization is a relatively minor one, and from a practical point of view may be of no significance. In graft polymerization, the newly formed polymer is covalently bonded to a site on the host polymer (PET), while the in situ bulk polymerization of a vinyl monomer results in a polymer that is physically entraped in the PET. The vinyl polymerization in the PET is usually carried out in the presence of the swelling solvent, thereby maintaining the swollen PET structure during polymerization. The swollen structure allows the monomer to diffuse in sufficient quantities to react at the active centers that have been produced by chemical initiation (with AIBM) before termination takes place. 

Resin 3 is light orange in color when dry 5 is tan. Both turn dark brown in a swelling solvent. Exposure of either resin to air slowly results in a grey-green color due to oxidation, but 28% of the resin-bound Cp0o(C0)2 is left after one month s exposure (IR). 

Although the cross-linked pyrazoline polymer is insoluble in common organic solvents by virtue of the crosslinks present, it was discovered that films of this material could be cast onto a variety of substrates from a suspension in a swelling solvent such as benzene. The ability to cast films is presumably related to the substantial change in polymer resin morphology after the coupling reaction has proceeded. The initial resin is hard, spherical and white in color, while the reacted bead is powdery, irregular in appearance and yellow, the color of the pyrazoline monomer. 

A study of the reaction kinetics of the reaction of butyl isocyanate with wood has been performed (West and Banks, 1986 West and Banks, 1987). Reactions were performed without catalyst and using pyridine, triethylamine, 1,4-diazobicyclo [2,2,2-octane] or di-butyl-tin-diacetate as catalyst. The data showed that no catalyst was effective without the presence of a swelling solvent. Kinetic profiles were obtained, which were deconvo-luted to yield two component reaction curves. It was considered that these two curves represented reaction with lignin and the holocellulose component of the cell wall. 

Use the largest interstitial volumes (large bead sizes). Use swelling solvents. 

According to Flory-Huggins theory, in the limit of x the critical x parameter is 0.5.(H) Below this value the polymer and solvent will be miscible in all proportions. Above this value, the solvent will not dissolve the polymer, but will act only as a swelling solvent. Thus, the pure solvent may not dissolve the polymer even though it is not crosslinked. If x is not , the critical value of x is larger, but the same qualitative arguments regarding mutual solubility of the solvent and polymer hold. Thus, the application of Equation 1 does not require that the pure solvent be able to completely dissolve the polymer, only that the solvent dissolve into the polymer by an amount that can be measured. 

Intraparticle diffusion limits rates in triphase catalysis whenever the reaction is fast enough to prevent attaiment of an equilibrium distribution of reactant throughout the gel catalyst. Numerous experimental parameters affect intraparticle diffusion. If mass transfer is not rate-limiting, particle size effects on observed rates can be attributed entirely to intraparticle diffusion. Polymer % cross-linking (% CL), % ring substitution (% RS), swelling solvent, and the size of reactant molecule all can affect both intrinsic reactivity and intraparticle diffusion. Typical particle size effects on the... 

Another important property of open-cell PolyHIPE materials is their ability to absorb large quantities of solvent, by capillary action [128]. Simply immersing a piece of the material in the liquid causes absorption, with displacement of the air from inside the matrix. This occurs until all voids are filled. The nature of the liquid will affect the volume which can be taken up [133]. Methanol, which is a non-swelling solvent for crosslinked polystyrene, is absorbed to a lesser... 

DMF is a good swelling solvent, the reaction does not proceed to completion due to the poor solubility of the reagents in that medium. The reagents have better solubility in DMSO, but use of 2 1 DMF-DMSO did not improve the reaction yield. Pyridine, which is a better solvent for the reagent and a good swelling solvent for polystyrene resin, was ultimately shown to be the best solvent tested. 

It has to be emphasized that x2 is an intrinsic parameter of the network. Its value should be the same in the unswollen state and in the presence of any swelling solvent. 

If such a network with labelled chains is studied in the presence of various swelling solvents, the product pQ 1 3 is found to vary far beyond experimental error, contrary to the product d )-1 3, discussed above. This result was however expected if Gaussian statistics is applied to a chain the ends of which are maintained at a distance d, the radius of gyration of that chain can be expressed as32 ... 

Another possible choice for the reference state is the equilibrium swelling degree of the network. In that case the thermodynamic characteristics of the actual polymer-swelling solvent system would be taken into account. However this choice does not consider the conditions of network formation. Moreover when the gel is swollen to equilibrium, the elastic chains are extended with respect to the corresponding free chains, and the extension ratio is not easy to evaluate13. ... 

Since the reduced modulus G refers to the unswollen, unstrained, isotropic network, the question arises, first, whether it should be the same for a given network, regardless of the swelling solvent. It was found that for PDMS networks as well as for polystyrene networks the value of G is not the same for a given gel whatever the swelling solvent may be14,22. This result, which implies that the swelling solvent influ-... 

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