Interface polymer-transparent solid

Reagents and indicators are immobilized, occluded or dissolved in supports which are formed by cross-linked polymers, plasticized polymers or organic and inorganic activated surfaces. The waveguide itself, the cladding of an optical fiber or any other optical element can be the support. However, it must obey two basic functions act as a liquid-solid or gas-solid interface and, if radiation crosses through it to allow the signal transmission, be an optically transparent material. 

Up to date, besides the SFA, several non-interferometric techniques have been developed for direct measurements of surface forces between solid surfaces. The most popular and widespread is atomic force microscopy, AFM [14]. This technique has been refined for surface forces measurements by introducing the colloidal probe technique [15,16], The AFM colloidal probe method is, compared to the SFA, rapid and allows for considerable flexibility with respect to the used substrates, taken into account that there is no requirement for the surfaces to be neither transparent, nor atomically smooth over macroscopic areas. However, it suffers an inherent drawback as compared to the SFA It is not possible to determine the absolute distance between the surfaces, which is a serious limitation, especially in studies of soft interfaces, such as, e.g., polymer adsorption layers. Another interesting surface forces technique that deserves attention is measurement and analysis of surface and interaction forces (MASIF), developed by Parker [17]. This technique allows measurement of interaction between two macroscopic surfaces and uses a bimorph as a force sensor. In analogy to the AFM, this technique allows for rapid measurements and expands flexibility with respect to substrate choice however, it fails if the absolute distance resolution is required. 

The changes in polymer appearance after exposure to aqueous media were evaluated using light and SEM microscopy. Before exposure to buffer, the polymer is transparent. After exposure to buffer the polymer became opaque, and when it was cut, two different regions were found the outer region which is gel and the core, which appears as a soft solid matrix. SEM analysis of the interface of the polymer exposed to buffer showed that a kind of a rigid network was formed across the polymer sample. This network causes the polymer drop to keep its shape in water. 

Polymer-dispersed liquid crystals (PDLCs) are important to liquid-crystal technology. Nematic LC microdroplets are dispersed in a polymer matrix. These films are used similarly to liquid crystal displays such as displays, switchable windows, and light shutters. PDLC devices operate on the principle of electrical modulation of the LC refractive index to match or mismatch the refractive index of an optically transparent, isotropic solid. PDLC films are made between conductive, transparent substrates, and can be switched from being opaque to being transparent with the application of an electric field. Solid state NMR methods have been used to study (PCLCs) and to identify the LC/polymer interface [80,81]. Using NMR one can iden-... 

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