Methacrylic backbones

Polymers studied, in most cases methacrylic backbones were used. 

Polymers with flexible spacer groups. Polymers obtained by precipitation or by casting films from solutions were found to be amorphous as shown by X-ray and microscopical observations. The DSC data revealed that on heating up the samples for the first time a stepwise increase of the specific heat occurred which could be attributed to a glass transition. Thus at room temperature the as received samples were in the isotropic glassy state, apparently no liquid crystalline solutions exist. 

The melting points of the polymers studied were in the range of 100 to 130 deg. C for polymers 1 and around 200 deg. C for polymers 2. 

At the glass transition a distinct stepwise change of the specific heat was only observed for nematic phases whereas for the case of the smectic phase only a change in the slope of the specific heat temperature curve was found. Additional techniques such as dilate-metry have to be used in order to prove that actually a glass transition occurs. This result indicates that since the smectic structure is closer to that of a crystal, the motions which take place above the glass transition will be restricted. Thus the increase in the specific heat will be small. The types of motions which freeze in at the glass transition will be discussed below. 

Isotropic glasses are characterized by relaxation processes, which are directly related to the nonequilibrium nature of the glassy state. Similar processes should also occur in liquid crystalline glasses. Enthalpy relaxation was observed for samples, which had been annealed below the glass transition temperature for several hours, proving the non-equilibrium nature of smectic and nematic glasses. 

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The hydrogens of the methylene group in the backbone of the poly (methyl methacrylate) produce a single peak in a racemic dyad, as illustrated by structure [XVI]. 

Mechanical Properties Related to Polymer Structure. Methacrylates are harder polymers of higher tensile strength and lower elongation than thek acrylate counterparts because substitution of the methyl group for the a-hydrogen on the main chain restricts the freedom of rotation and motion of the polymer backbone. This is demonstrated in Table 3. 

Increa sing the bulkiness of the alkyl group from the esterifying alcohol in the ester also restricts the motion of backbone polymer chains past each other, as evidenced by an increase in the T within a series of isomers. In Table 1, note the increase in T of poly(isopropyl methacrylate) over the / -propyl ester and similar trends within the butyl series. The member of the butyl series with the bulkiest alcohol chain, poly(/-butyl methacrylate), has a T (107°C) almost identical to that of poly(methyl methacrylate) (Tg = 105° C), whereas the butyl isomer with the most flexible alcohol chain, poly( -butyl methaciylate), has a T of 20°C. Further increase in the rigidity and bulk of the side chain increases the T. An example is poly(isobomyl methacrylate)... 

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

The melt viscosity of a polymer at a given temperature is a measure of the rate at which chains can move relative to each other. This will be controlled by the ease of rotation about the backbone bonds, i.e. the chain flexibility, and on the degree of entanglement. Because of their low chain flexibility, polymers such as polytetrafluoroethylene, the aromatic polyimides, the aromatic polycarbonates and to a less extent poly(vinyl chloride) and poly(methyl methacrylate) are highly viscous in their melting range as compared with polyethylene and polystyrene. 

Notable among the alternative materials are the MBS polymers, in which methyl methacrylate and styrene are grafted on to the polybutadiene backbone. This has resulted in two clear-cut advantages over ABS. The polymers could be made with high clarity and they had better resistance to discolouration in the presence of ultraviolet light. Disadvantages of MBS systems are that they have lower tensile strength and heat deflection temperature under load. 

Hybrid systems of acrylics with other technologies have been reported. Aciylic and epoxy polymers can be coupled through the use of 2-methacryloloxyethyl phosphate. The phosphoric acid functionality reacts with epoxy and the methacrylate group copolymerizes with the acrylic backbone [ 145] (Scheme 14). 

Methacrylates and acrylates are readily synthesized from low-cost commercially available resins and (meth)acrylate intermediates or (meth)acrylic acid [19]. A wide range of structural backbones are available, including epoxies, urethanes. 

The methacrylic backbone structure makes the spherical Toyopearl particles rigid, which in turn allows linear pressure flow curves up to nearly 120 psi (<10 bar), as seen in Fig. 4.45. Toyopearl HW resins are highly resistant to chemical and microbial attack and are stable over a wide pH range (pH 2-12 for operation, and from pH 1 to 13 for routine cleaning and sanitization). Toyopearl HW resins are compatible with solvents such as methanol, ethanol, acetone, isopropanol, -propanol, and chloroform. Toyopearl HW media have been used with harsh denaturants such as guanidine chloride, sodium dodecyl sulfate, and urea with no loss of efficiency or resolution (40). Studies in which Toyopearl HW media were exposed to 50% trifluoroacetic acid at 40°C for 4 weeks revealed no change in the retention of various proteins. Similarly, the repeated exposure of Toyopearl HW-55S to 0.1 N NaOH did not change retention times or efficiencies for marker compounds (41). 

The presence of sulphonic and carboxylic groups enables the iron ions to be in the vicinity of the cellulose backbone chain. In this case, the radicals formed can easily attack the cellulose chain leading to the formation of a cellulose macroradical. Grafting of methyl methacrylate on tertiary aminized cotton using the bi-sulphite-hydrogen peroxide redox system was also investigated [58]. 

Grafting reactions onto a polymer backbone with a polymeric initiator have recently been reported by Hazer [56-60]. Active polystyrene [56], active polymethyl methacrylate [57], or macroazoinitiator [58,59] was mixed with a biopolyester polyhydroxynonanaate [60] (PHN) or polybutadiene to be carried out by thermal grafting reactions. The grafting reactions of PHN with polymer radicals may proceed by H-abstraction from the tertier carbon atom in the same manner as free radical modification reactions of polypropylene or polyhy-droxybutyratevalerate [61,62]. 

Using these macroinitiators PDMS-polystyrene and PDMS-poly(methyl methacrylate) multiblock copolymers were synthesized 305). Due to the backbone Structure of these macroinitiators and their thermolysis mechanisms, the copolymers obtained... 

Such a sequence is very pronounced with the different stereoisomers of poly(methyl methacrylate), for example, and is a reflection of the increasingly easy rotation about the backbone C—C bonds in the different configurations. 

II. B polyethylene glycol, ethylene oxide, polystyrene, diisocyanates (urethanes), polyvinylchloride, chloroprene, THF, diglycolide, dilac-tide, <5-valerolactone, substituted e-caprolactones, 4-vinyl anisole, styrene, methyl methacrylate, and vinyl acetate. In addition to these species, many copolymers have been prepared from oligomers of PCL. In particular, a variety of polyester-urethanes have been synthesized from hydroxy-terminated PCL, some of which have achieved commercial status (9). Graft copolymers with acrylic acid, acrylonitrile, and styrene have been prepared using PCL as the backbone polymer (60). 

Solubilization of a graft copolymer comprising a hydrophobic poly(dodecyl-methacrylate) backbone and hydrophilic poly(ethylene glycol) monomethyl ether side chains in water/AOT/cyclohexane w/o microemulsions was rationalized in terms of the backbone dissolved in the continuous apolar phase and the side chains entrapped within the aqueous micellar cores [189],... 

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). 

In our own research, the functional termination of the living siloxanolate with a chlorosilane functional methacrylate leading to siloxane macromonomers with number average molecular weights from 1000 to 20,000 g/mole has been emphasized. Methacrylic and styrenic monomers were then copolymerized with these macromonomers to produce graft copolymers where the styrenic or acrylic monomers comprise the backbone, and the siloxane chains are pendant as grafts as depicted in Scheme 1. Copolymers were prepared with siloxane contents from 5 to 50 weight percent. 

Morphological studies were conducted on model copolymers containing a methyl methacrylate backbone and approximately... 

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