Polymerization of HEMA

Also, included in these formulations are water-soluble initiators/activators for the polymerization of HEMA. 

Two matrices are formed a metal polyacrylate salt and a polymer. There is a lack of water in the system because some of it has been replaced by HEM A, and lack of water in glass polyalkenoate cements is known to slow down the ionomer add-base reaction (Hornsby, 1977). Thus, the initial set of these materials results from the polymerization of HEMA and not the characteristic acid-base reaction of glass-ionomer cements. The later reaction serves only to harden and strengthen the already formed matrix. 

Polymerization of HEMA incorporated in the PET films is dependent both on the initiator concentration and reaction temperature. In order to overcome the low initiation efficiency inside the PET, due to the low mobility of the free radicals formed inside the PET structure, as well as that of the monomer itself, high initiator concentrations were used. The results are listed in Table II. However, satisfactory conversions of HEMA in pHEMA were obtained only when the polymerization was carried out at 80-85°C for 20-40 hr, even if the initiator concentration was high (Figure 3). 

Table II. Polymerization of HEMA Incorporated in PET Films Treated in DMF (140°C/l5 min)...

LAI QUINN Initiator Diluent Effects on Polymerization of HEMA... 

Figure 5. The proposed template effect of glycerine on the polymerization of HEMA.

Fig. 8. Activity of immobilized antibody by the radiation polymerization method as a function of antigen concentration. Antigen a-fetoprotein. Antibody anti-a-fetoprotein. Immobilization method polymerization of HEMA in a thin porous membrane O polymerization of HEMA in particle form...

V. Tertykh, Yu. Bol bukh, and V. Yanishpolskii, Effect of unmodified and surface treated fumed silica on the polymerization of HEMA, Macromol. Symp. 221(1), 145-152 (2005). 

Methanol is a good solvent for HEMA and its polymer, and thus can be employed for its homogeneous living radical polymerization with Ru-3, which is also highly soluble in methanol.59 Copper-based systems also give homogeneous living radical polymerizations of HEMA in a mixture of methyl ethyl ketone and 1-propanol,243 of acrylamides in methanol,117172 and of 4-vinylpyridine (M-33) in 2-pro-panol.214... 

Polymerization of HEMA is affected by the presence of the other components of resin-modified glass-ionomers. It has been shown that HEMA itself will undergo addition polymerization more rapidly in the presence of poly(acrylic acid) than on its own [18]. However, in resin-modified glass-ionomers, pure unreacted poly(acrylic acid) may not be present for very long, and the effect of metal polyacrylate salts on the rate of polymerization of HEMA has not been studied. 

Sergeyeva et al. [90,91] had introduced a very promising improvement by using an oligourethane-acrylate macromonomer in imprinting polymerization mixtures in order to increase the flexibility and mechanical stability of the membranes self-supported MIP membranes with a thickness between 60 and 120 pm could be prepared. Sreenivasan [92] had also addressed the problem of film stability, and a semi-IPN film was prepared by the polymerization of HEMA in a blend with polyurethane. 

Polyhydroxyethylmethacrylate (PHEMA)-Zr02 nanohybrid materials were prepared in a one-step process by mixing zirconium aUcoxide and 2-hydroxyethyl methacrylate (HEMA) with or without benzoyl peroxide (BPO) [184]. Also, monolithic nanohybrid materials were prepared via in-situ polymerization of HEMA in... 

Introduction of HEMA, and more precisely the introduction of hydroxyl groups using graft polymerization of HEMA onto PHBHV surface in presence of benzoyl peroxide as chemical initiator (BPO), increased the surface hydrophiUcity of PHBHV. The extent of grafting can be modulated by the preparation conditions, particularly the monomer concentration [70]. The most convenient technique for modifying the... 

Laser-induced surface grafting of poly(HEMA) and a sequential method for preparation of NPNs of PDMS/ poly(HEMA) were used by Abbasi et al. [79] for surface and bulk modifications, respectively. Data from in-vitro results showed that platelet adhesion is greatly reduced by the surface graft polymerization of HEMA in comparison with the control sample. The above research team concluded that if other functions are not required, surface modification may be preferred to bulk modification however, for the design of PDMS devices with potential for limited swelling, bulk modification may be preferred to surface modification. 

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