Solvent induced swelling

Both solvent-induced swelling and oxygen inhibition are characteristic of all cross-linking negative resists based on free-radical chemistry. 

The linear dependence of uptake on time results from the existence of a cleaily dis-cernable propagating solvent-induced swelling front which moves thrmi the pconstant velocity. The polymer ahead of the front is largely free of penetrant, while the polymer behind the front has essentially reached its equilibrium swelling value corresponding to the temperature and pressure of the experiment. For Fickian... 

Ogiwara, Kubota, and Yasunaga (23) have examined the effect of fiber swelling, photosensitizer, and solvent on photo-induced graft polymerization of methyl methacrylate on vinyl, nylon 6, and polyester fibers. Solvent-induced swelling of fiber as well as the presence of certain sensitizers were found to increase photo-induced grafting through enhancement of radical formation on the fibers. 

Brenner, D. 1984. Microscopic in-situ studies of the solvent induced swelling of thin sections of coal. Fuel, 63 1325. 

An important observation is that when powder samples of N2 and NIO are exposed to isooctane or methanol at room teiiq[>erature and then cooled to 77 K, the phosphorescence decay times are substantially longer than the dry powder sample. This result points to solvent-induced swelling of the PM phases during sample preparation leading to increased N/N pair separations. These differences are maintained when the sample is cooled. ... 

It was shown (8,9) that the pretreatment of PET yarns with certain strongly interacting solvents can lead not only to swelling but also to irreversible modifications of polymers structure. The basis of structural modification during the DMF treatment of PET is solvent-induced crystallization which occurs while the PET structure is swollen by DMF. At low treatment temperatures (i.e., 50-100°C, Table I), only small crystallites are formed and after removal of the solvent the swollen structure cannot be supported by the small crystallites and consequently collapses. 

Theoretical Predictions and Molecular Parameters. As previously emphasized (21, 22), a major and unique virtue of the simple zeroth-order theory is that it makes many experimentally testable predictions. More-sophisticated versions of the theory, which include physical effects such as rotational defect interactions, solvent-induced polymer swelling, and polydispersity, have been constructed (21). However, the basic features of the theory are not very sensitive to these complications (21, 22). This encourages us to believe that the predictions extracted from the simplest version of the theory may have wide validity. In this section, we explicitly enumerate and illustrate, with our polysilylene results, the various predictions. 

One of the major hmitations of coated polysaccharide-type CSPs is their incompatibility with so-called non-standard solvents. Specifically, the exposure of coated CSPs to dichloromethane, chlororform, ethyl acetate, tetrahydrofuran, dioxane, toluene and acetone, induces swelling and/or dissolution of the physically adsorbed polymer films and thus destruction of fhe columns. To address this serious drawback, a considerable amount of research has focused on the development of immobihzed versions with global solvent compatibility. In the last two decades numerous immobilization strategies have been reported [126], and the quest for solvent-stable versions capable of reproducing with fidelity the excellent separation characteristics of their coated congeners is still an active field of study [100, 127-130]. Reported immobilization approaches capitalize on (i) surface at-... 

The model equations were numerically solved using a finite difference technique. The predicted movement of the interfaces, R and S, with respect to time is shown in Fig. 27. The corresponding concentration profile is shown in Fig. 28. These results show the existence of three distinct stages in the dissolution process. In the first stage, there is solvent-penetration inducing swelling... 

Two major changes are associated with the redox switching process in ECPs one is the charge of the polymer chains that induce ionic motion to maintain electroneutrality (and in the particular case of PANI, possibly proton exchange [179]) the other one is related to the hydrophobic/hydrophUic balance of the polymer matrix that makes the solvent play an important role in the doping process and often induce swelling phenomena [180]. It has been shown that counterion insertion during oxidation of PPy is accompanied by desolvation processes as evidenced by variation of the diffusion coefficient of the counterion [181]. These desolvation processes could be involved in the achievement of the quasi-metallic state of ECP [182]. 

A membrane is classified as porous when the void volumes within the membrane exceed 50% of the membrane volume. The porous membranes can be generated from the dense membranes by addition of a solvent that induces swelling. The solvent can be evaporated from some membranes to leave large, stable voids within the porous membrane. The surfaces of these porous membranes can also be modified to produce a skin with the desired selectivity and permeability properties. 

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