Based on polymer swelling

Fiber optic sensors based on polymer swelling offer several potential advantages. They can be designed so that the optical measurement is separated from the polymer by a diaphragm so that the measurement can not be affected by the optical properties of the sample. Unlike fiber optic sensors based on indicator absorbance or luminescence, photodegradation is not a potential source of sensor instability. Measurements can be made in the near infrared region of the spectrum and take advantage of inexpensive components available for fiber optic communications. 

It is reasonably easy to use Eq. 26 to determine the solubility parameter of a solvent, but since the heat of vaporization of polymers is usually not known, other methods are needed to determine the solubility parameters of polymers. There are several experimental methods, based on polymer swelling measurements or on the determination of the intrinsic viscosity of polymer solutions. Alternatively, solubility parameters can be predicted from knowledge of the chemical structure of each component. The latter method is due to Small (72) and Hoy (73), who supplied values for molar attraction constants (G) of a large number of functional groups (Table 4). The constants G are additive. With these values it is possible to estimate the solubility parameter of any polymer using Eq. 28, where p represents the density and M the molecular weight of the polymer. 

Figure 20.3.4. Schematic diagram representing the synthetic process-mixture of components in a heterogeneous solid phase (A), the Udocaine-based DES (B), the lidocaine-loaded prepolymer (C), and elastomer (D), and the lidocaine release based on polymer swelling and degradation [Adapted, by permission, from M.

Another system was based on a swelling core tablet and a surrounding coating consisting of a combination of hydrophobic and hydrophilic polymers. The insoluble hydrophilic polymer, such as calcium pectinate or calcium alginate, was dispersed in the coating and served as a channel-former in order to control the water penetration. The core contained a swelling, but... 

Endolysosomal escape has also been demonstrated by various endosomoly-tic polymers [186-188] using the proton sponge hypothesis, which is based on osmotic swelling of the vesicle via buffering of the endosomal environment. Under these conditions, the endosomal membrane will rupture, leading to the release of drugs into the cytoplasm. 

Glucose changes also affect the osmotic strength of interstitial fluid, and sensors based on chemical swelling or shrinking of polymers, optical changes in the refractive index, and osmotic effects on electrochemical capacitance have been refined through in vitro studies. Prospective clinical trials are needed to more clearly identify the potential of these approaches. 

Goikfl Method for determining the G value of o %aa-linking of a polymer based on the swelling of the cross-linked gel... 

A further refinement of such a classification system has been put forward based on the compatibiUty between elastomeric materials and fluids as set out in ISO/DIS.6072. This proposal by Nagdi is based on the swelling behaviour of an elastomer in specified fluids, relating the swell results to those of a known standard compound. The refinement in this method means that more precise definition of the elastomers being used in a seal is made, the polymer base being identified. 

This equation may be used for the estimation of the swelling capacity of the activated seed particles with the monomer. A typical graph sketched based on Eq. (11) is given in Fig. 18. This graph shows the variation of the swelling capacity of the seed polymer particles VmIVp) with the ratio of interfacial tension-initial particle radius... 

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