Grafting, polymer

Polymer grafting of CNCs surfaces is performed using two ways (1) grafting onto and (2) grafting from [136]. 

The well-defined surface functionalization using classical organic reactions plays an important role in membrane development. In order to be susceptible to reaction, the polymer chain should contain double bonds, hydroxyl groups or benzene rings. An example is the modification of polysulfone by reaction with different chemicals to increase hydrophilicity. The surface modification of polysulfone membranes has been reported by several authors [120, 121]. 

Grafting of hydrophilic vinyl monomers, such as hydroxyethyl methacrylate on polysulfone and PAN membranes under UV exposure to make them less susceptible to fouling, has been described in the literature [129, 130]. 

Photografting has also been reported as a strategy to prepare membranes for affinity separation [145]. Functionalization of PAN has been reported for the manufacture of molecular imprinted membranes for molecular recognition. The membranes are prepared in the presence of selected templates, which are then removed leading to the formation of complementary imprinted sites [146, 147]. 

The incorporation of positive charges has decreased the fouling susceptibility of membranes even more effectively. This is the principle of the aromatic polyamide membrane series commercialized by Hydranautics as low fouling composite membranes (LFC). Cationic charge-modified nylon membranes are also commercially available from CUNO 3M, under the trademark Zeta Plus . Pall Corp. sells cationic charge-modified nylon membranes under the trademark Ngg Posidyne. There are different ways to make the membrane positively charged. A patent from Millipore [148] describes the surface modification of hydrophobic membranes by contacting them with a solution of polyamine epichlorohydrin 

PPy S alkyl S alkoxy S hydroxyalkyl S caiboxyalkyl S alkyl sulfonic add S amine S ester group 

PTh S alkyl S alkoxy S ester group S alkthio S carboxyl alkyl 

Soutve Reprinted from Bai and Shi (2001). Published by MDPl PEB poly(diethylyl benzene) 

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Grafting of polymers Graft polymerization Graft versus host disease Grahamite Graham s salt Grain... 

Coagents ate often used with peroxides to increase the state of cure. Some coagents, such as polybutadiene or multifimctional methacrylates, are used at high levels to form polymer grafts or interpenetrating networks. Other coagents such as triaHyl cyanurate, triaHyl trimelHtate, and y /i -phenjiene bismaleimide are used at low levels to reduce the tendency of the polymer to degrade by chain scission. 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

Hyperbranched Polymers Grafted from Planar Surfaces. 28... 

Hyperbranched Polymers Grafted from Spherical Particles. 31... 

Fig. 15. Schematic representation of the synthesis of hyperbranched, branched, and linear polymers grafted from functionalized silicon wafers SFM images and XPS spectra of the surface-grafted polymers. (Reproduced with permission from [48],Copyright 2001 American Chemical Society.)...

Y Okahata, H Noguchi, T Seki. Functional capsule membranes. 26. Permeability control of polymer-grafted capsule membranes responding to ambient pH changes. Macromolecules 20 15-21, 1987. 

PNIPAM-co-GMA (Table 1). Thus, different distributions of substituents are possible, in principle. It was of interest to see (1) whether the distribution of the PEO grafts on the PNIPAM main chain influences the thermal properties of the polymer and (2) whether the polymer grafted at elevated temperature adopted the collapsed conformation in which it was synthesised when its aqueous solution was heated. 

Preparation and Stability of Polymer-Grafted Silica Dispersions... 

For both kinds of polymer-grafted particles, flocculation was induced either by changing the temperature or by adding a nonsolvent for the stabilising polymer. In this way critical flocculation temperature (c.f.T) and critical flocculation vol. fractions of non-solvent (c.f.v.) values were obtained, in general as a function of . 

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