Methacrylic acid-ethylene glycol templates

A similar concept was used in the development of artificial chymotrypsin mimics [54]. The esterase-site was modeled by using the phosphonate template 75 as a stable transition state analogue (Scheme 13.19). The catalytic triad of the active site of chymotrypsin - that is, serine, histidine and aspartic acid (carboxy-late anion) - was mimicked by imidazole, phenolic hydroxy and carboxyl groups, respectively. The catalytically active MIP catalyst 76 was prepared using free radical polymerization, in the presence of the phosphonate template 75, methacrylic acid, ethylene glycol dimethacrylate and AIBN. The template removal conditions had a decisive influence on the efficiency of the polymer-mediated catalysis, and best results were obtained with aqueous Na2CC>3. 

Mosbach and co-workers developed a method to prepare molecularly imprinted polymers by precipitation polymerization [24]. They started from a dilute, homogenous solution of the monomer methacrylic acid (MAA) and the crosslinker trimethylolpropane trimethacrylate (TRIM) or ethylene glycol dimethacrylate (EGDMA). The polymer formed in the presence of the template molecule 17/1-estradiol, theophylline, or caffeine contained a high proportion of discrete spheres of diameter less than a micron. Because the effect of coalescence becomes predominant with higher solid content of the reaction mixture, this approach is limited to solid contents of typically <2 wt%. 

The typical mole ratio of atrazine, methacrylic acid, and ethylene glycol dimethacrylate in chloroform is 1 3-5 25-30. Although the adduct is formed from one atrazine and two methacrylic acids (Fig. 6.2), the atrazine/methacrylic acid ratio in the mixtures is usually kept around 4 to move the equilibrium toward the formation of these hydrogen-bonding adducts. The mole ratio of crosslinking agent to the template is in general 20-30. 

An ultrathin-film composite membrane selective for theophylline has been reported [48]. The theophylline-imprinted polymer was prepared inside pores of a microporous alumina support membrane with a thickness of 500 nm and a pore size of 20 nm, in which pores of the membrane were filled by the polymerization solution containing the template theophylline, methacrylic acid, and ethylene glycol dimethacrylate, and the membrane was illuminated with UV light for 1 h, followed by immersion in methanol containing 10 %(v/v) acetic acid to remove the template and any excess monomer. Because the membrane is extremely thin, the flux rate is high, being at least two orders of mag-... 

Matsui et al. [162] first reported the preparation of molecularly imprinted monoliths based on functional monomer such as methacrylic acid or 2-trifluoromethyl-acrylic acid via in situ polymerization. The reaction mixture consisting of monomer, cross-linker (ethylene glycol dimethacrylate), porogenic solvents (cyclohexanol and 1-dodecanol), initiator, and template molecule was degassed and poured into a column where the polymerization took place. When reaction is completed, the template molecule and the porogenic solvents were extracted with methanol and acetic acid resulting in monoliths with molecular recognition in the separation of positional isomers of diaminonaphthalene and phenylalanine anilide enantiomers. 

The fact that a large number of templates has been successfully imprinted using basic recipes has led to the proliferation of MIPs of relatively low complexity, most of which have been based on a restricted number of synthetic trials (even though in some cases supported by spectroscopic or computational hints). The majority of basic templates have been imprinted using methacrylic acid (MAA) as monomer (seeTable 5.6A in Ref. 1), the acidic ones using vinylpyridines (VPY) (seeTable 5.6B in Ref 1). Ethylene glycol dimethacrylate (EDMA) is the most used crosslinker (see Table 2.5 in Ref 1), acetonitrile, dichloromethane, chloroform, toluene the most used solvents. 

Imprinted polymer membranes are prepared using atrazine as the template, methacrylic acid as a functional monomer, and tri(ethylene glycol) dimethacrylate (TEDMA) as a cross-linker. The molar ratio of the functional monomer to the template is 5 1. This ratio has to be optimized for each template. In order to obtain thin, flexible and mechanically stable membranes, oligourethane acrylate (molecular mass 2600) is added to the monomer mixture. Preparation of the molecularly imprinted polymer membrane is done as follows. Atrazine (20 mg) is mixed with methacrylic acid (40 mg), TEDMA (289 mg), oligourethane acrylate (51 mg), AIBN (2 mg) and 30% v/v of chloroform. Then a 60-120 pm gap between two quartz slides is filled with the monomer mixture. To initiate polymerization, the slides with the mixture are exposed to UV radiation (365 nm, intensity 20 W m ) for 30 min. After polymerization, atrazine is extracted with ethanol in a Soxhlet apparatus for 2h. This should not cause any visible changes in the MIP membrane. A membrane for control experiments can be prepared similarly except that no atrazine is added to the monomer mixture. 

An interesting case of template pol5unerization was described by Pa-pisov and co-workers (47-49). The authors used two templates with different strengths of interaction with respect to the daughter polymer. The first template was poly(vinylpyrrolidinone) and the second, poly(ethylene glycol monolaurate). Methacrylic acid was used as a monomer. 

By a surface imprinting technique, in Zhang H. et al., 2011, a comfX)site imprinted material, on the basis of a MWCNTs-incorporated layer using melamine as a template, methacrylic acid as a functional monomer, and ethylene glycol dimethaciylate as a cross-linker, was synthesized. In this work, the poly(acrylic-acid)-functionalized CNTs were synthesized to increase the diameter of CNTs. Then, the vinyl group was introduced to the surface of poly(acrylic-acid)-functionalized CNTs by an amidation Using Melamine as a template molecule, imprinted CNT composite material was fabricated by a thermal fX)lymeiization. Applied as a sorbent, the imprinted materials were used for the determination of Melamine in the spiked sample by online SPE combined with HPLC. 

Papisov et a/. have examined the influence of templates consisting of poly-(ethylene glycol)+poly(JV-vinylpyrrolidone) and poly(vinyl alcohol)+polyvinylpyrrolidone) on the polymerization of acrylic and methacrylic acids in aqueous solution at 50 °C. Growing chains of poly(methaciylic acid) apparently complex preferentially with poly(iV-vinylpyrrolidone) the order of complexing strength is given as poly(A/-vinylpyrrolidone) > poly(ethylene glycol) > poly-(vinyl alcohol). 

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