Alkyl-Grafted Surfaces

Although open tubular columns have been used for RPLC,42 most applications use packed columns. The most widely used column packings are formed by chemically bonding butyl (C4), octyl (C8), or octadecyl (C18) chains to a silica surface. Phenyl (Ph), cyano (CN), and amino (NH2) functionalities are also used. Polymeric packings which are finding broad acceptance include alkyl-grafted poly(methylmethacrylate) and alkyl-grafted or unmodified... 

Recently, alkylchitosans were prepared giving interesting amphiphilic properties due to physical network formed by hydrophobic interaction between alkyl grafted chains they also have surface activity. [104-106] Grafting of N-isopropylaciylamide (NIPAm) or a ethylene oxide-propylene oxide copolymer (POEP) on chitosan produces thermosensitive polymers which may have new applications in controlled release. [107,108]An other thermosensitive systems was obtained when a glycerol-2-phosphate solution is added to a solution of chitosan up to pH around 7 the gel forms over 37°C. [109-111]... 

Photoinduced free radical graft copolymerization onto a polymer surface can be accomplished by several different techniques. The simplest method is to expose the polymer surface (P-RH) to UV light in the presence of a vinyl monomer (M). Alkyl radicals formed, e.g. due to main chain scission or other reactions at the polymer surface can then initiate graft polymerization by addition of monomer (Scheme 1). Homopolymer is also initiated (HRM-). 

The synthesis of group 4 alkoxide complexes grafted on the surface of silica illustrates this approach.44-47 Two routes were considered, which are schematically represented in Equations(2) and (3) they differ in the nature of the precursor complex, which is either the tetra-alkoxide M(OR)4 (Equation(2)), or the tetra-alkyl complex MR4, M = Ti, Zr, Hf (Equation(3)) ... 

A new class of amphiphilic, surface-active graft copolymers, hydrophobically modified hydroxyethyl celluloses (HM-HEC s), are comprised of a cellulose backbone with short polyethylene oxide (PEO) and grafted alkyl side chains. They are excellent steric stabilizers of 0/W emulsions. 

Triflic acid has also been supported on a porous silica carrier (220). The authors emphasized the importance of a strong interaction between the acid and the support to prevent leaching of the acid. In pulsed liquid-phase isobutane/ 1-butene alkylation experiments at 298 K, the catalysts produced a very high-quality alkylate, made up almost exclusively of isooctanes. With silanol groups on the silica surface or with added water, triflic acid was found to form a monohydrate that was firmly grafted to the silica surface. 

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