Polymers in Confined Space of Pores

Interactions of ID polymers with porous solid particles depend on many factors types (chemistry) of a polymer and a solid, textural, and morphological characteristics of solid particles (5, V, PSD, particle size), dispersion medium (solvent can be a strong competitor especially in narrow pores), concentration, temperature, and time of interactions. In this case, the confined space effects can play a much stronger role than in the case of nanooxides composed of nonporous nanoparticles. A polymer shell on adsorbent particles can form a strong barrier (thick cross-linked 3D strictures) or a semipermeable membrane (thin 2D structures at a lower degree of cross-linking). Core-shell 

NMR spectroscopy data showed that the order of C30 alkyl chains (after reaction of C30 trichlorosilane with oxide surfaces) is higher on titania (5bet= 17 mVg, Vp=0.12 cmVg, pore size fi =28.6 nm) and zirconia (31 m /g, 0.23 cmVg, 29 mn) than on silica (77 and 109 m /g, 0.74 and 0.9 cmVg, 30 and 26 nm) microparticles ( 3 pm in size for all) (Pursch et al. 2000). The C30 self-assembled monolayers (SAM) are thicker (4.05 nm) than that of Cjg SAM (2.82 nm). 

Mirau et al. (1999) used the H MAS NMR to study a low acrylate polymer in bulk and polymerized in a Vycor glass with 4 nm pores (250 m /g, porosity 0.28). The combination of chain motion and fast MAS averaged the proton-proton dipolar interactions such that high-resolution spectra were observed at ambient temperature. Multiple-quantum NMR showed that some of the chains were severely restricted relative to the bulk material due to confined effects in narrow mesopores of the glass. These restricted chains could be returned to their bulk-like state by surface treatment of the porous glass. 

Nuclear Magnetic Resonance Studies of Interfacial Phenomena 

Pyrocarbon/nanosUica samples were synthesized by pyrolysis of CHjClj on nanosilica A-300 (5 bet=295 m /g) at 773 K for 40 min (CS4, Cq=4 wt%) or 823 K for 90 min (CS40, Cq=40 wt%) (Leboda et al. 2001c). CS4 and CS40 have the specific surface area of 280 and 160 mVg, respectively. The surfaces of CS4 possess mosaic structures with pyrocarbon patches on oxide particles, individnal carbon particles of 10-50 nm and free silica surfaces, but in the case of CS40, practically entire surfaces of silica particles are covered by carbon deposits. PEG (Ferak) with molecular weight 1250 was used as received. 

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