Microgels and process for their preparation

A process for forming a microgel which comprise a core of crosslinked polymer and multiplicity of substantially linear polymeric arms attached to the core;

• wherein the process comprises
• (a) polymerizing monoethylencically unsaturated mononmers in the presence of a thiocarbonylthio chain transfer agent to form a prepolymer containing a thiocarbonylthio group that has a weight average molecular weight of 1,000-25,000;
• (b) polymerizing said prepolymer with monnmers of the core comprising monoethylenically unsaturated monomers and 0.5-60 mole percent, based on the total moles of monomer of the core, of multi-olefinic polymerizable monomers containing two or more carbon-carbon double bonds which are crosslinked in the core, to form the microgel having a weight average molecular weight of 104-108;
• wherein the monethylenically unsaturated monomers of the core and the prepolymer are individually selected from the group consisting of alkenes having 2-10 carbon atoms, alkyl (meth)acrylates having 1-12 carbon atoms in the alkyl group, hydroxyakyl (meth)acrylate, wherein the alkyl groups have 1-4 carbons atoms, styrene, alkylstyrene, acrylonitrile,glycidyl (meth)acrylate, isobornyl (meth)acrylate, alpha-beta ethylenically unsaturated monocarboxylic acids, haloalkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, N-substituted aminoalkyl(meth)acrylates, N,N-di-substituted aminoalkyl (meth)acrylates, cycloalkyl (meth)acrylates, phenyl (meth)acrylate, alkylene glycol (meth)acrylate, poly(alkylene glycol) (meth)acrylate, acrylamides, methacrylamides, esters of fumaric acid, esters of maleic acid, maleic acid, maleic acid anhydride, N-vinylcarbazole, N-vinylpyrrolidone, vinylpyridine, benzyl (meth)acrylate, vinyl acetate, vinyl chloride, vinylindene chloride, butadiene, isoprene, chloroprene and any mixtures thereof;
• and wherein the thiocarbonylthio transfer agent is selected from the group
• wherein:
• Z is selected from the group consisting of hydrogen, chlorine, alkyl and subsitituted aryl, aryl and substituted aryl, heterocyclic ring and substituted heterocyclic ring, alkythio and substituted alkylthio, arylthio and substituted arylthio, alkoxy and substituted alkoxy, aryloxy and substituted aryloxy, amino and substituted amino, alkoxycarbonyl and substituted alkoxycarbonyl, aryloxycarbonyl and substituted aryloxycarbonyl, carboxy, acyloxy and substituted acyloxy, aroyloxy and substituted aroyloxy, carbamoyl and substituted carbamoyl, cyano, dialky- and diaryl-phosphonato, dialkyl-phosphinato and diaryl-phosphinato, and a polymer chain;
• R7 is selected from the group consisting of alkyl and substituted alkyl, alkenyl and substituted alkenyl, alkynyl and substituted alkynyl, saturated, unsaturated and aromatic carbocyclic ring, saturated, unsaturated aromatic heterocylic ring, alkylthio and substituted alkylthio group, and a polymer chain, such that R7 forms free radical leaving group that can initiate free radical polymerization under the reaction conditions;
• n is an integer greater than 1;
• R7′ is an n-valent moiety derived from R7 and Z′ is an n valent moiety derived from a species selected from the group consisting alkyl and substituted alkyl, aryl and substituted aryl and a polymer chain where the connecting moieties are selected from the group consisting of aliphatic carbon, aromatic carbon, oxygen and sulfur;
• and
• wherein the substituents for the substituted moieties for R7, R7′, Z and Z′ are selected from the group consisting of hydroxy, tertiary amino, halogen, cyano, epoxy, carboxylic acid, alkoxy, alkyl having 1-32 carbon atoms, aryl, alkenyl having 2-32 carbon atoms, alkynyl having from 2-32 carbon atoms, saturated carbocyclic rings having 3-14 carbon atoms, unsaturated carbocyclic rings having 4-14 carbon atoms, aromatic carbocyclic rings having 6-14 carbon atoms, saturated heterocyclic rings having 3-14 carbon atoms unsaturated heterocyclic rings having 4-14 carbon atoms and aromatic carbocyclic rings having 4-14 carbon atoms.