Cross-linking methacrylate copolymers

Elliott Jeannine E., and Bowman Christopher N. Effects of solvent quality during polymerization on network structure of cross-linked methacrylate copolymers. J. Phys. Chem. B 106 no. 11 (2002) 2843-2847. 

Allyl methacrylate and allyl acrylate are difunctional monomers, triallyl phosphate is a trifunctional monomer, and polyethylene glycol dimethacrylate is a polyfunctional monomer. All these lead to cross-linked graft copolymers. 

Y. Amagi, M. Ohya, Z. Shiiki, and H. Yusa, PVC Blended with Cross-linked Graft Copolymers of Styrene and Methyl Methacrylate onto a Butadiene Polymer, U.S. Pat. 3,775,514 (1973). MBS resins in latex form. Triple IPN in latex form. Clear, impact-resistant PVC. 

Fig.l. Modulus—temperature curve of amorphous and cross-linked methacrylic polymers A, a softer polymer B, a harder polymer and C, a 1 1 copolymer of A and B. 

Systematic studies on photo-cross-linking block copolymer micelles, with a core of poly(cinnamoylethyl methacrylate) (PCEMA) were published by Liu and co-workers [229]. With PAA as the shell-forming block, these authors could demonstrate by SLS, DLS, TEM and SEC that photo-cross-linking of PCEMA locked in the initial structure of the micelles without any significant change in their aggregation number and size distribution. Corecross-linking of PEO-PMAA micellar systems with Ca ions has recently been described by Kabanov and co-workers [230]. 

Park et al. investigated the influence of the structure of the polymer on the activity of PS-immobilized IL [50]. They immobilized ammonium-based IL on three types of chloromethylated PS (FSl, PS2, and PS3), and used the immobilized IL catalysts for the reaction of CO2 and glycidyl methacrylate. PSl is a soluble copolymer prepared from ST and VBC. Both PS2 and PS3 are the cross-linked (insoluble) copolymers prepared from ST, DVB, and VBC, but the latter had macropores which were generated by addition of isooctyl alcohol to the mixture of ST, DVB and VBC before the copolymeiization and the consecutive extraction of the alcohol by methanol after the pwlymerization. The product yield depended on the structure of the support polymer. It was in the order of PSl > PS3 > PS2, which could be expected by considering the accessibility of the substrates to the IL active site. 

The polymer-encapsulated MWNTs have been successfully prepared through ultrasonically initiated in situ emulsion polymerizations of n-butyl acrylate (BA) and methyl methacrylate (MMA) in the presence of MWNTs. Another noncovalent method for functionalization of SWNTs was also developed by encasing the SWNTs within cross-linked, amphiphilic copolymer micelles. This encapsulation significantly improves the dispersion of SWNTs in a wide variety of polar and nonpolar solvents and polymer matrices. ... 

The use of hydroxyethyl (also hydroxypropyl) methacrylate as a monomer permits the introduction of reactive hydroxyl groups into the copolymers. This offers the possibility for subsequent cross-linking with an HO-reactive difunctional agent (diisocyanate, diepoxide, or melamine-formaldehyde resin). Hydroxyl groups promote adhesion to polar substrates. 

Use of dimethylaminoethyl (also rert-butylaminoethyl) methacrylate as a monomer permits the introduction of pendent amino groups which can serve as sites for secondary cross-linking, provide a way to make the copolymer acid-soluble, and provide anchoring sites for dyes and pigments. 

Other Polymers. Besides polycarbonates, poly(methyl methacrylate)s, cycfic polyolefins, and uv-curable cross-linked polymers, a host of other polymers have been examined for their suitabiUty as substrate materials for optical data storage, preferably compact disks, in the last years. These polymers have not gained commercial importance polystyrene (PS), poly(vinyl chloride) (PVC), cellulose acetobutyrate (CAB), bis(diallylpolycarbonate) (BDPC), poly(ethylene terephthalate) (PET), styrene—acrylonitrile copolymers (SAN), poly(vinyl acetate) (PVAC), and for substrates with high resistance to heat softening, polysulfones (PSU) and polyimides (PI). 

Fig. 26. Qualitative compatison of substrate materials for optical disks (187) An = birefringence IS = impact strength BM = bending modulus HDT = heat distortion temperature Met = metallizability WA = water absorption Proc = processibility. The materials are bisphenol A—polycarbonate (BPA-PC), copolymer (20 80) of BPA-PC and trimethylcyclohexane—polycarbonate (TMC-PC), poly(methyl methacrylate) (PMMA), uv-curable cross-linked polymer (uv-DM), cycHc polyolefins (CPO), and, for comparison, glass.

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

When the polymer was prepared by the suspension polymerization technique, the product was crosslinked beads of unusually uniform size (see Fig. 16 for SEM picture of the beads) with hydrophobic surface characteristics. This shows that cardanyl acrylate/methacry-late can be used as comonomers-cum-cross-linking agents in vinyl polymerizations. This further gives rise to more opportunities to prepare polymer supports for synthesis particularly for experiments in solid-state peptide synthesis. Polymer supports based on activated acrylates have recently been reported to be useful in supported organic reactions, metal ion separation, etc. [198,199]. Copolymers are expected to give better performance and, hence, coplymers of CA and CM A with methyl methacrylate (MMA), styrene (St), and acrylonitrile (AN) were prepared and characterized [196,197]. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Polymers with a sizable number of ionic groups and a relatively nonpolar backbone are known as ionomers. The term was first used for copolymers of ethylene with carboxylated monomers (such as methacrylic acid) present as salts, and cross-linked thermoreversibly by divalent metal ions. Such polymers are useful as transparent packaging and coating materials. Their fluorinated forms have been made into very interesting ion-exchange membranes (considered further below). 

The IR spectra of thin films from an alternating copolymer of tri-n-butyl-stannyl methacrylate and maleic anhydride at various stages of UV irradiation were also studied l09). It can be expected that cross-linking results in hindered rotational and oscillatory mobility of the backbone chain and of side chains in the macromolecule. Indeed, a decrease in the peak intensity of most absorption bands is observed in the IR spectra of an irradiated copolymer 1770 and 1840 cm-1 (vc=0 anhydride), 1406 cm-1 (Sq, in CH2—Sn), 1285 and 1080 cm-1 (vc 0 c), 1115, 850, 750cm-1, etc. At the same time, there is an increase in the intensity of absorption bands near 1720 (vc=0 in — COOSnR3) and 1580 cm-1 (vc Q in -C=Q... SnRa). 

Poly(butyl methacrylate) (PBMA) began to be used as a picture varnish in the early 1930s. It encountered a considerable success because of its resistance to yellowing, adequate flexibility, no dirt pick-up and good solubility in nonpolar hydrocarbon solvents. Products based on PBMA, such as Elvacite 2044 and Elvacite 2045 by Du Pont, were abandoned when it was discovered that under light exposure they cross-link to an unexpected extent becoming insoluble [64]. From this point of view acrylic copolymers based on methyl and ethyl acrylates/methacrylates show a much better long-term stability. 

Previous work on allyl methacrylate homopolymers and statistical copolymers clearly showed that the allyl group is a very effective cross-linking function when exposed to x-rays (2) ... 

Cross-linked copolymers of hydroxyethyl methacrylate and methyl methacrylate are slightly swollen by water and are used as soft contact lenses. 

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