Chemically joined, phase separated self-cured hydrophilic thermoplastic graft copolymers and their preparation

A chemically joined, phase separated selfcured hydrophilic thermoplastic graft copolymer of:

• 1. at least one copolymerizable normally hydrophobic macromolecular monomer having a substantially uniform molecular weight distribution, and
• 2. at least one copolymerizable comonomer which is rendered hydrophilic forming the polymeric backbone of said copolymer, said copolymerizable normally hydrophobic macromolecular monomer forming linear polymeric sidechains of said graft copolymer, wherein:
• a. the polymeric backbones of the graft copolymer are comprised of polymerized units of said copolymerizable comonomers, wherein the copolymerizable comonomers are selected from the group consisting of vinyl esters of monocarboxylic acids which are rendered hydrophilic by hydrolysis of said vinyl esters subsequent to copolymerization, and mixtures thereof;
• b. the linear polymeric sidechains of the graft copolymer consist essentially of a polymerized hydrophobic macromolecular monomer, said hydrophobic macromolecular monomer comprising a linear polymer or copolymer having a molecular weight of at least about 2,000 and having a substantially uniform molecular weight distribution, such that its ratio of Mw/Mn is not substantially above about 1.1, said macromolecular monomer being further characterized as having no more than one copolymerizable moiety per linear polymer or copolymer chain, said copolymerization occurring between the copolymerizable end group of said hydrophobic macromolecular monomer and said copolymerizable hydrophilic comonomer;
• and
• c. the linear polymeric sidechains of the graft copolymer which are copolymerized into the copolymeric backbone are separated by at least about 20 uninterrupted recurring monomeric units of said hydrophilic polymeric backbone, the distribution of the sidechains along the backbone and the copolymerization being controlled by the reactivity ratios of the copolymerizable end group on said hydrophobic macromolecular monomer and said copolymerizable hydrophilic comonomer.

A process for preparing a chemically joined, phase separated self-cured hydrophilic thermoplastic graft copolymer comprising:

• 1. copolymerizing:
• a. at least one copolymerizable normally hydrophobic macromolecular monomer comprising a linear polymer or copolymer having a molecular weight of at least about 2,000 and having a substantially uniform molecular weight distribution, such that its ratio of Mw/Mn is not substantially above about 1.1, said macromolecular monomer being further characterized as having no more than one copolymerizable moiety per linear polymer or copolymer chain, said copolymerizable moiety being on the end of the chain;
• and
• b. at least one copolymerizable comonomer, said copolymerizable comonomer forming the polymeric backbones of said graft copolymer and said copolymerizable normally hydrophobic macromolecular monomer forming the linear polymeric sidechains of said graft copolymer, and the linear polymeric sidechains of the graft copolymer are copolymerized into the backbone polymer through the polymerizable end group on said macromolecular monomer, and wherein said copolymerizable comonomer units of the backbone are comprised of a polymerized vinyl ester of a monocarboxylic acid, the linear polymeric sidechains of the graft copolymer which are copolymerized into the copolymeric backbone being separated by at least about 20 uninterrupted recurring monomeric units of said backbone polymer;
• the copolymerization and distribution of the sidechains along the backbone polymers being controlled by the relative reactivity ratios of the copolymerizable end group on said hydrophobic macromolecular monomer and said copolymerizable comonomer;
• and
• 2. saponifying the resulting copolymer to thereby obtain said chemically joined, phase separated self-cured hydrophilic thermoplastic graft copolymer.