Methacrylate forms

The lack of solvent separated pairs raises the question whether some alternative mode of solvation should be considered. The ester group of the penultimate unit of the polymer, or the one preceeding it, could act as a solvating agent. The idea of intramolecular solvation was proposed by several workers in the field 37) and it is supported by the results of nmr studies of polymethyl methacrylate formed under various experimental conditions 38). Hypothetical structures such as those depicted below were proposed 39 h... 

Polymerization of t-butyl methacrylate initiated by lithium compounds in toluene yields 100% isotactic polymers 64,65), and significantly, of a nearly uniform molecular-weight, while the isotactic polymethyl methacrylate formed under these conditions has a bimodal distribution. Significantly, the propagation of the lithium pairs of the t-Bu ester carbanion, is faster in toluene than in THF. In hydrocarbon solvents the monomers seem to interact strongly with the Li+ cations in the transition state of the addition, while the conventional direct monomer interaction with carbanions, that requires partial dissociation of ion-pair in the transition state of propagation, governs the addition in ethereal solvents. 

Three main types of polymer-based monoliths are polymethacrylate-based monoliths where methacrylate forms the major component of the monomers for polymerization, polyacrylamide-based monoliths where cross-linked polyacrylamide is synthesized directly within the capillary, and polystyrene-based monoliths that are usually prepared from styrene and 4-(chloromethyl) styrene as monomers and divinylbenzene (DVB) as the cross-linker. 

Mixtures of poly(vinylidene fluoride) with poly (methyl methacrylate) and with poly (ethyl methacrylate) form compatible blends. As evidence of compatibility, single glass transition temperatures are observed for the mixtures, and transparency is observed over a broad range of composition. These criteria, in combination, are acceptable evidence for true molecular intermixing (1, 19). These systems are particularly interesting in view of Bohns (1) review, in which he concludes that a compatible mixture of one crystalline polymer with any other polymer is unlikely except in the remotely possible case of mixed crystal formation. In the present case, the crystalline PVdF is effectively dissolved into the amorphous methacrylate polymer melt, and the dissolved, now amorphous, PVdF behaves as a plasticizer for the glassy methacrylate polymers. 

E.g., by joint acetylation of methyl- and phenyltrichlorosilanes with phenyltrichlorosilane one can obtain a mixture of triacetoxymethyl- and phenylsilanes, which after methacrylation forms a mixture of silanes with methacrylethyl groups at the silicon atom, apart from the acetate ones. 

In later communications (27, 28) Hirooka reported that in addition to acrylonitrile, other conjugated monomers such as methyl acrylate and methyl methacrylate formed active complexes with organoaluminum halides, and the latter yielded high molecular weight 1 1 alternating copolymers with styrene and ethylene. However, an unconjugated monomer such as vinyl acetate failed to copolymerize with olefins by this technique. 

The stereospecificity of poly(methyl methacrylate) formed after initiation by Grignard or organolithium compounds depends on the solvent, temperature, halogen, and the organic initiator component. A change in any of these factors leads to a substantial change in stereostructure [86, 87]. Also... 

While steric hindrance may play a role in decreasing rates and molecular weights in dimethyl itaconate polymerization, the limited effect of initiator concentration on molecular weights as measured by the intrinsic viscosity suggests other factors must be present. Pol5unethyl methacrylate formed at 60° with benzoyl peroxide initiator shows an inverse proportionality of degree of polymerization with polymerization rate as ifrould be expected kinetically for bimolecular termination. 

Comments methyl methacrylate forms the basis of acrylic bone cements used in orthopedic surgery. 

Poly(vinyls) substituted with -OH, -O-R, -OC(0)-R, -C(0)-R, -C5H4N, etc. groups form one important class of synthetic polymers having saturated carbon chain backbone. Other polymers derived from the vinyl group with specific substituents such as poly(halogenated olefins), poly(styrenes), poly(acrylates), and poly(methacrylates) form their own classes and are not included here. Examples of polymers known as poly(vinyls) and discussed in this section have formulas as indicated below ... 

Poly(acrylates) and poly(methacrylates) form another class of common polymers with saturated carbon chain backbone. Polyacrylates can be considered vinyl polymers with the -COOR group attached at every other carbon atom in the chain. However, due to their common use and particular properties, polyacrylates form a separate polymer class together with polymethacrylates. Among the most common polymers from this class are those obtained from acrylic acid methyl ester (PMA) and methylacrylic (methacrylic) acid methyl ester (PMMA). Acrylic polymers have many practical applications in automotive industry, in the production of medical materials, paints, coatings and lacquers, adhesives, textiles, and synthetic leather. Poly(methacrylic acid methyl ester) can be obtained in cast sheets with applications in technical components, furniture, building materials, etc. Formulas for poly(acrylic acid), two polyacrylates, and poly(methyl methacrylate) are shown below ... 

Methyl methacrylate forms a polymer, a colorless liquid insoluble in water and glass-like, that is used in manufacturing contact lenses and shatterproof glass. 

Unfortunately, this kind of discrimination is unfeasible in the polymethyl methacrylate system. However, the tactidty of the polymer provides a useful way of differentiating between these two alternatives. The polymethyl methacrylate formed in THF by monofunctional initiators is, to a high degree, syndiotactic. The tacticity should have remained unaltered had the association-dissociation mechanism been operative, whereas the polymer formed in the early stages of a reaction initiated by bifunctional initiators shows a larger proportion of isotactic diads. This demonstrates that the slow addition involves a different center, i.e. it takes place on the associated end-groups. A further discussion of tacticity is postponed here and will be continued later. 

In toluene solution, syndiotactic block copolymers of methyl methacrylate (PMMA) and allyl methacrylate were formed using triphenylphosphine and triethylaluminum as initiator [76]. In acetone solution, syndiotactic poly(methyl methacrylate) forms a stereocomplex with other syndiotactic polymers. The complex formed with syndiotactic poly(allyl methacrylate), upon separation from the reaction mixture and drying had a melting point of 141.5°C by DSC thermogram. From X-ray powder patterns of this and related complexes of PMMA with other polymethacrylates, the authors postulate that a double-stranded helix may represent a model of the structure of these complexes [77]. 

Synthetic polymer, poly(triphenylmethyl methacrylate) forms a helical structure similar to that of cellulose chirality arises from the twist of the helix with one enantiomer being formed because of the use of a chiral initiator in the polymerisation. 

Sodium montmorilonite can also be used to polymerize polar monomers between the lamellae. Here, too, the organization of monomer molecules within the monolayers influences the structure of the resultant polymers. Poly (methyl methacrylate) formed in sodium montmorilonite is composed of short, predominantly isotactic stereosequences. The percent of isotactic component... 

Solvents influence the rate of free-radical homopolymerization of acrylic acid and its copolymerization with other monomers. Hydrogen-bonding solvents slow down the reaction rates. Due to the electron-withdrawing nature of the ester groups, acrylic and methacrylic ester polymerize by anionic but not by cationic mechanisms. Lithium alkyls are very effective initiators of a-methyl methacrylate polymerization yielding stereospecific polymers.Isotactic poly(methyl methacrylate) forms in hydrocarbon solvents. Block copolymers of isotactic and syndiotactic poly(methyl methacrylate) form in solvents of medium polarity. Syndiotactic polymers form in polar solvents, like ethylene glycol dimethyl ether, or pyridine. This solvent influence is related to Lewis basicity in the following order ... 

Finally, the unsaturated polyester is free-radically cross-linked by copolymerization with, for example, styrene or methyl methacrylate. Mixtures of the actual unsaturated polyester with these monomers are commercially known as unsaturated polyester resins. The properties of the thermosets can be matched to the application by variations in the acids, glycols, or vinyl monomers. Copolymerization with electronegative comonomers such as styrene or vinyl acetate leads, for example, to alternating copolymers, that is, to short cross-link bridges and therefore, to more rigid thermosets. Alternatively, electropositive comonomers such as methyl methacrylate form long methyl methacrylate bridges between the polyester chains and so produce more flexible polymerizates. 

Polymethyl methacrylate forms a condensed film when it is spread at the air/ water interface and this polymer has been analysed by SQELS by the same two... 

Polymerizations of polar monomers, like acrylic and methacrylic esters with alkyllithium initiators yield the greatest amount of steric control [151]. An almost all isotactic poly(methyl methacrylate) forms at low temperatures. Addition of Lewis bases such as ethers or amines reduces the degree of isotactic placement. Depending upon the temperature, atactic or syndiotactic polymers form [151]. Also, butyllithium in heptane yields an isotactic poly(A, iV -dibutyla-crylamide) at room temperature [201]. 

Methacrylates form an important class of monomers. They are available with a large number of different ester side groups. NMP is not capable of polymerizing methacrylates in a controlled fashion. Most frequently the nitroxide will imdergo a disproportionation reaction, with the propagating radical leading to a dead polymer chain with an unsaturated chain end and a hydroxylamine. 

Intramolecular Repulsive Interactions. Miscible blends can also be achieved in absence of specific interactions, by exploiting the so-called intramolecular repulsive effect. This is observed in mixtures where at least one of the components is a statistical copolymer miscibility is restricted to a miscibility window, that is, it takes place within a well-defined range of copolymer composition. For example, poly(styrene-co-acrylonitrile) (SAN) and poly(methyl methacrylate) form miscible blends for copolymer compositions in the range 9-39% acrylonitrile (26,27). Miscibility in these systems is not a result of specific interactions but it is due to the intramolecular repulsive effect (28) between the two monomer units in the copol5uner such that, by mixing with a third component, these imfavorable contacts are minimized. The same situation is encoimtered in binary mixtures of two copol5uners (29). 

Isotactic and syndiotactic poly(methyi methacrylate) form a stereocomplex and this has been investigated by isolating crystalline complexes from dilute solution. ... 

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