SELF-THREADING-BASE APPROACH FOR BRANCHED AND OR CROSS-LINKED POLY(METHACRYLATE ROTAXANE)S/

Physically branched and cross-linked polymeric structures were produce d for the first time by rotaxane formation during reaction of a pendan t group of a preformed macromolecule. The rotaxane structure is believ ed to form from a hydrogen-bonded bimolecular complex of ymethyl)-1,3- phenylene-1',3'-phenylene-32-crown-10 (16) by esterification of the hy droxy group of one macrocycle through the cavity of the second in its reaction with poly(methacryloyl chloride) (12). For esters formed in m odel reactions of 12 with methanol and with 5-(hydroxymethyl)-1,3-phen ylene-16-crown-5 (14), which is too small to be threaded, the degrees of polymerization were identical; however, the polymer from reaction o f 12 and 16 under the same conditions had a significantly higher degre e of polymerization and polydispersity, i.e., was highly branched via rotaxane formation. Increasing the concentration in the reaction of 12 with 16 led to the formation of a gel fraction along with a high mole cular weight sol fraction; the gel represents a novel network structur e based on mechanical interlocking via rotaxane structures. 2D NOESY N MR experiments clearly demonstrated the rotaxane structure as manifest in the through-space correlation of the benzylic protons of the ''thr ead'' with the intra-annular protons of the ''bead''.