D. G. Hawthorne

Copolymerization of ω-unsaturated oligo(methyl methacrylate): new macromonomers

Abstract The free-radical copolymerization of ω-unsaturated oligo(methyl methacrylate) (1) with each of ethyl acrylate, styrene, methyl methacrylate, acrylonitrile, and vinyl acetate have been investigated. Incorporation of (1) into the polymer was observed in all cases although the molecular weights of the copolymers were substantially lower than those of the homopolymers obtained in the absence of (1) but under otherwise identical conditions. These experiments, together with a product study of the reactions of (1) with cyanoisopropyl radicals, have shown that the addition of free radicals to the double bond of (1) occurs readily. The sterically hindered radical so formed, however, undergoes facile β-scission, resulting in the termination of chains (chain transfer) in competition with chain propagation. The implications of these findings to the usefulness of (1) in the synthesis of graft copolymers and their relevance to the chemistry of free-radical polymerizations when methyl methacrylate is employed a...

Cyclopolymerization of Diallylamines

Abstract Interest in the polymerization of diallylamines and various substituted diallylamines, including triallylamine, has been stimulated by the successful industrial development of flocculants [l] and “Sirotherm” ion-exchange resins [2] based on these polymer systerns. The polymers also have potential applications in such diverse areas as fiber [3] and paper [4] technology, and in the sequestration of heavy-metal cations [5]. The free radical induced polymerization diallylamines (1), like that of other 1,6-dienes (7), has been shown to proceed by a series of alternate intra-intermolecular additions with the formation of chains comprising pyrrolidine (5) and/or piper-idine (6) derived moieties (Scheme 1) [6]. This process of polymerization via a series of alternate intra-intermolecular additions is known as cyclopolymerization [7]. Polymers derived from diallylamines are not only of commercial significance, but are also of scientific interest as their polymerization mechanisms raise a number of points ...

Polymerization of Vinyl Monomers on Mineral Surfaces; A Novel Method of Preparing Reinforcing Fillers

Abstract A novel method for producing modified mineral fillers is reported: The mineral surface is first made “acidic” and this acidic surface is used to initiate the cationic polymerization of vinyl or preferably divinyl monomers, the residual acidic sites being subsequently neutralized with ammonia or an organic base. During compounding, grafting occurs between the encapsulating polymer layer and the matrix polymer via previously formed peroxidic groups in this layer or via radical attachment at unsaturated centers in the polymer coating. The incorporation of these modified fillers in various grades of polyethylene results in significant improvements in processability and in tensile and impact strength relative to the properties of equivalent composites using untreated or merely hydrophobic fillers.

Reinforcement of Polyethylene by Surface-Modified Kaolins

Abstract The tensile and impact strength of kaolin-filled polyethylene was found to be dependant on the modulus of the matrix in the vicinity of the filler surfaces and the strength of the filler-matrix bonds, as well as on the degree of dispersion of the kaolin particles on the polyethylene. Improved reinforcement was obtained by the use of novel fillers consisting of kaolin particles encapsulated with high-modulus, surface-bonded, reactive oxyaluminum acylate polymers.

Cyclopolymerization. IX. Effect of β-Substituents on the Cyclopolymerization of Diallylamines

Abstract ESR studies and analysis of the products from the cyclopolymerization of substituted diallylamines show that the cyclization may not involve a concerted process, and that the proportion of piperidine rings formed is increased by the use of bulky or conjugated β-substituents, or increased reaction temperatures, factors which favor thermodynamic control of the direction of ring closure. Increased piperidine ring content causes a small reduction in the basicity of the polymers.

Cyclopolymerization. IV. Low Molecular Weight Products for the Reactions of Allylamines and Diallylamines with Azobisisobutyronitrile

Abstract The azobisisobutyronitrile-initiated polymerization of various N-substituted diallylammonium, N-ethyldimethallylammonium, and triallylammonium chlorides yielded as the respective major by-products 2-substituted 6, 6-dimethylperhydro-5-isoindolones, 2-ethyl-3a, 6,6,7a-tetramethylperhydro-5-isoindolone, and 2-allyl-6,6-dimethylperhydro-5-isoindolone. These isoindolones are formed from pyrrolidylmethylene radical precursors and indicate that, in agreement with recent ESR studies, radical addition to diallylamines results in the formation of pyrrolidine derivatives and not piperidines as previously supposed. The reactions of azobisisobutyronitrile and azobisis-obutyramidine dihydrochloride with the models, N,N-dimethylallylammonium and N,N,2-trimethylallylammonium chlorides, are also described.

The Reaction of 2,2-Diphenyl-1-picrylhydrazyl with Minerals

Abstract 2,2-Diphenyl-1-picrylhydrazyl (DPPH) is reversibly adsorbed at acidic centers on the surfaces of a variety of common mineral pigments and fillers, and undergoes a subsequent irreversible reaction with adsorbed water or surface hydroxy groups to yield 1,1-diphenyl-2-picrylhydrazine, 1-(4′-nitrophenyl)-1-phenyl-2-picrylhydrazine, and 4,4′-oxybis[N-(4-picryliminocyclohexa-2,5-dienylidene)aniline] as the major products. The rate of the irreversible reaction on kaolinite is second-order with respect to DPPH and probably depends on the disproportionation between a DPPH and a protonated DPPH molecule. The possible use of DPPH as a probe for the activity of mineral fillers in polymer chemistry, and some implications on its use as a diagnostic test for radical species are discussed.

Cyanoisopropyl radical induced cyclization and cyclopolymerization of N-methyl-N-(2-alkylallyl)amines and N-methyl-NN-bis-(2-alkylallyl)amines. A 13C nuclear magnetic resonance study

The structures of the cyclic products from the cyanoisopropyl radical induced cyclization and cyclo-polymerization of N-methyl-N-allyl-N-(2-alkylallyl)amines and N-methyl-NN-bis-(2-alkylallyl)amines are shown by 13C n.m.r. spectroscopy to be pyrrolidines and piperidines, the proportion of each depending upon the bulk of the 2-alkyl substituent.