文档介绍：Synthesis, Characterization and Properties of Octa-Arm
Polyisobutylene-Based Star Polymers
Sunny Jacob, Joseph P. Kennedy
The Maurice Morton Institute of Polymer Science, The University of Akron, Akron,
Ohio 44325–3909, USA
e-mail: ******@
This review concerns the synthesis, characterization, and select properties of a series of
novel eight-arm polyisobutylene (PIB)-based stars. An octafunctional initiator containing
2-methoxyisopropyl groups 1 was synthesized by quantitative functionalization of 5,11,
17,23,29,35,41,47-octaacetyl-49,50,51,52,53,54,55,56-octamethoxy-calix[8]arene and used
to prepare the stars. Stars with PIB arms, terminally functionalized PIB arms, poly(styrene-
b-isobutylene) (PSt-b-PIB) arms, and poly(p-chlorostyrene-b-isobutylene) (PpClSt-b-PIB)
arms were synthesized. Polymerizations of isobutylene (IB) to prepare well-defined PIB
stars were effected by the use of octa-functional initiator with BCl3-TiCl4 coinitiators in two
stages. Stage I was carried out in the presence of a fraction of the required amount of IB in
CH3Cl and polymerization was induced by the addition of BCl3. Stage II was induced by the
addition of TiCl4 and the balance of IB, and the polymerization was carried pletion.
The relative concentrations of BCl3 and TiCl4 were critical for the synthesis of well-defined
stars. By the use of well-chosen BCl3-TiCl4 concentrations, added in sequence in two stages,
narrow dispersity stars, MMwn/.,=111 were prepared. Gel permeation chromatography
(GPC), with on-line RI, UV, and laser light scattering (LLS) detectors, was used to deter-
mine the molecular weights positions of linear and octa-arm star polymers. The
number of arms of the stars was determined by 1H NMR spectroscopy and by selective core
destruction. Both studies indicated that the number of arms was close to the theoretical val-
ue of eight. The mechanism of polymerization was studied by the use of a model monofunc-
tional analogue of