Monitoring Block-Copolymer Crossover-Chemistry in ROMP: Catalyst Evaluation via Mass-Spectrometry (MALDI)

Abstract

We report on the monitoring and evaluation of the crossover reaction in ring-opening metathesis polymerization (ROMP) via MALDI methods. ROMP of various monomers using several catalytic systems (first-generation ( I ) and third-generation Grubbs-type ( III )) was investigated with structurally different norbornene monomers derived from (±) endo, exo -bicyclo[2,2,1]-hept-5-ene-2,3-dicarboxylic acid-bis- O -methyl ester (monomer A ), (±) endo, exo -bicyclo[2,2,1]-hept-5-ene-2,3-dicarboxylic acid-bis- O -2,2,6,6-tetramethyl piperidinoxyl-ester (monomer T ), (±) exo - N -(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)-10-oxa-4-azatricyclodec-8-ene-3,5-dione (monomer D ), and the highly strained monomer 2-methyl-2-phenyl-cyclopropene (monomer E ). The crossover reactions as well as the polymerization kinetics of the various monomers were studied in detail, in particular, using matrix-assisted laser desorption ionization mass spectrometry (MALDI). Catalyst III offered access to the synthesis of highly defined block copolymers, generating poly( A - b - T ), poly( A - b - D ), and poly( A - b - E ) diblockcopolymers in high precision, whereas catalyst I offered access to the diblockcopolymers poly( A - b - D ) and poly( A - b - E ). Poly( A ) was used as a probe to analyze the crossover reaction, revealing well-defined crossover kinetics in the case of monomers T, D, and E and a subsequent good polymerization after the crossover reaction in the case of monomer E . The presented system allows a simple evaluation and monitoring of crossover reactions in ROMP-based polymerization reactions.