Benchmarking of ruthenium initiators for the ROMP of a norbornenedicarboxylic acid ester

The kinetic study of ring-opening metathesis polymerization (ROMP) of a diester functionalised norbornene derivative, (±)-exo,endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid diethyl ester, with a series of ruthenium benzylidene complexes revealed the applicability of these initiators for well defined polymerization reactions. Values for the rate of initiation as well as the rate of propagation of the initiators were determined and correlated to the molecular weight and polydispersity of the isolated polymers. As the only initiator providing an entry to virtually monodisperse polymers the classical “first generation Grubbs-catalyst” was identified, while N-heterocyclic carbene based initiators polymerized with a rate of propagation much higher than the rate of initiation yielding polymers with a broader molecular weight distribution.     

Surface modification of a silicate substrate by a “grafting from” methodology utilizing a perester initiator

The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylation of t-butyl peroxy-10-undecanoate with trichlorosilane. These radical initiators were covalently bound to the surface of silicate substrates by self-assembled monolayer (SAM) techniques. Several hydrophilic and hydrophobic acrylate monomers were successfully grafted onto the silicate substrate by in situ polymerization from the surface bound perester initiators. The polymer brushes were characterized by the ATR-IR, XPS, AFM and water contact angles. The results of the study indicate this “grafting from” technique can be used for the preparation of polymer layers with high graft density. While these surface-bound initiators function similarly to surface-bound azo initiators, the preparation of the surface-active perester is a simple, two-step synthesis.     

Identification of Initiator Fragments in Polyisobutylene by Nmr Spectroscopy

Abstract

Deuterated polyisobutylenes carrying protonated initiator fragments were prepared by the living polymerization technique employing perdeuterated isobutylene [CD₂=C(CD₃)₂] and select protonated initiators (see Scheme 1). The polymers were analyzed by ¹H- and ¹³C-NMR spectroscopy, and the resonances due to the protic initiator fragments were unequivocally assigned. The assignments of ¹³C-NMR signals were affected by the distortionless enhancement by polarization transfer mode of spectra accumulation.     

Synthesis of New Primary-Tertiary Alkyl Bisperoxides by Reaction of Tertiary Hydroperoxides with Bromoalkanesin a PTC System

Summary.  Syntheses of novel primary-tertiary bisperoxides were carried out under phase transfer catalysis conditions. The bisperoxides were obtained in good yields, the reaction times not exceeding four hours. Received January 15, 2001. Accepted (revised) February 9, 2001     

Synthesis of fluorinated polymers via ROMP: a review

This review is concerned with the work conducted in the Durham group during the last twenty years. It is specifically concerned with ROMP of fluorinated monomers with classical and well-defined initiators, with the synthesis of stereoregular polymers, block and stereoblock copolymers.     

Studies of end-groups in polystyrene using H NMR

Studies have been made by 400 MHz ¹H NMR of initiator fragments in polystyrene made by radical polymerization in solution at 60 °C. Azoisobutyronitrile, benzoyl peroxide and lauroyl peroxide have been used as initiators. The peaks arising from hydrogens in the end-groups have been recognized. They cause alterations in the ratio of “aromatic hydrogens” to “aliphatic hydrogens” for polystyrene.