Surface-initiated grafting polymerization

Fig. 7.12 En antiomer separation of racemic analytes achieved on silica-supported poly(frons-l, 2-diaminocyclohexane-diacryl-amide)-type CSPs prepared by surface-initiated graft polymerization. (A) temazepam, n-hexane/ethanol (50/50 v/v) (B) binaphthol, dichloromethane/methanol (97/3 v/v) ...

Uekusa T, Nagano S, Seki T. 2007. Unique molecular orientation in a smectic liquid crystalline film attained by surface initiated graft polymerization. Langmuir 23 4642. 

Surface graft modification includes direct graft polymerization modification and surface-initiated grafting polymerization modification. The former requires the particle surface to have active groups to copolymerize with other monomers, whereas the latter require that active groups to copolymerize with other monomers are generated from the grain surface by chemical or physical methods. 

Preparation of CNF/Synthetic Polymer Nanocomposite Materials by Surface-Initiated Graft Polymerization... 

Surfaces play crucial roles in many important properties, including optical, mechanical, thermodynamic, and chemical properties, and thus surface modification is an important issue. One of the effective surface modification methods is surface-initiated graft polymerization. Fukuda et used LRP... 

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-). 

Another example is the copper-catalyzed surface-initiated radical polymerization of MMA from S-7 at room temperature without addition of free initiator. The molecular weights and MWDs of the polymers were directly measured after removing the brushes from the surface. For example, the surface with 40 nm thickness had Mn of 68900 and MWDs of 1.45. A high graft density (180 A2/chain) and decreased surface roughens (0.54 nm) were observed. This method is free from solution and thermal polymerizations due to the absence of free initiators and a low polymerization temperature, which permits a simple washing step without Soxhlet extraction. 

This preliminary study has shown that radiation initiated graft polymerization and co-polymerizatlon on a polyolefin film surface can be achieved using the above described process with electron initiation. This process can be employed with a wide range of monomers. ... 

In recent years, many kinds of temperature-responsive PNIPAAm and its copolymer hydrogels with other acrylic monomers have been synthesized [142]. Besides being used for hydrogels, NIPAAm monomer can be grafted on to polymer substrates by electron beam, irradiation or UV-initiated graft polymerization to achieve special modification of polymer surfaces. Thus NIPAAm has been grafted on porous polymer films such as LDPE, PP, or polyamide films in order to prepare novel films for pervaporation of liquid mixtures or separation membranes [150,151]. 

Figure 5.18 CNT surface-initiated anionic polymerization of styrene (top), and representative TEM images of PS-grafted MWCNTs with PS layer thickness up to 30 nm. ...

FIGURE 6.8 (a) Schematic illustration of the procedure for the synthesis of polymeric capsules based on surface-initiated RAFT polymerization using silica nanoparticles as templates, (b) TEM image of polymer grafted silica nanoparticles, (c) SEM and (d) TEM images of the synthesized polymeric capsules. Source Huang et al. [15]. Reproduced with permission of American Chemical Society. 

Advanced grafting-from approaches use molecular control of the interface reaction. Pioneering work had been done by Wang et al. [32], who had synthesized a copolymer with photo-initiator side groups, prepared a membrane by wet PI , and finally performed a surface-initiated imprinting polymerization yielding an MIP membrane with a pronounced selectivity forTho over Caf... 

Currently, UV-initiated graft polymerization has been widely used for the surface modification of polymer manbranes in attempts to develop composite manbranes with enhanced resistance toward organic fouling and biofouling. As can be seen in Table 3.1, different hydrophilic monomers, such as Af-vinyl-2-pyrrolidone (NVP), A-vinylformamide (NVF), A-vinyl-caprolactam (NVC), 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AA), acrylamide (AAm), 2-acrylamidoglycolic acid (AAG),... 

UV-initiated graft polymerization of AA on the surface of a PES manbrane via the immersion method using a 365 nm wavelength UV lamp was studied (Abu Seman et al. 2010). It was shown that irreversible manbrane fouling with humic acids (HA) was reduced after modification due to the increase in the hydrophilicity and the negative surface charge of the modified manbranes. 

Based on the membrane surface properties and the HA properties, various researchers have attempted to change the membrane surface characteristics by surface modification. Different techniques have been performed, such as ion beam irradiation, plasma treatment, redox-initiated graft polymerization, photochemical grafting, and interfacial polymerization (IP). In this chapter, two surface modification techniques, IP and photochemical grafting, are discussed by means of experimental examples. The surface characteristics of the unmodified membrane and the modified membranes are studied and their relationships with irreversible fouling and NF performance are reported. 

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