Well-defined 8-armed polyisobutylene stars were synthesized using tertiary hydroxyl and tertiary methoxy derivatives of octafunctional initiators 5,11,17,23,29,35,41,47-octaacetyl-49,50 The homopolymers, 51,52,53,54,55,56-octamethoxycalix[8]arene (Scheme 21)79 were polymerized in two steps in the same reactor. First, the initiator was added to CH3Cl at -80 C along with BCl3 and 25% isobutylene (IB) monomer, followed by hexane, TiCl4, and the remaining monomers. SEC with online RI, UV, and low-angle laser light scattering (LALLS) detectors was used to determine the absolute molecular weight and composition of stars. The molecular weights obtained are close to those expected theoretically.
(PIB-b-PS)3 star-shaped block copolymers were synthesized by a sequential monomer addition method using ring-substituted tricumyl chlorides as initiators and TiCl4 as co-initiators. 80 Polymerization was carried out at -80 C in the presence of pyridine (electron donor) and 2,6-di-tert-butylpyridine (proton trap) in 60/40 (v/v) methylcyclohexane- Chloromethane solvent mixture. The synthesized copolymer exhibited a rather low PDI (1.17), and its mechanical, thermal and morphological properties were extensively examined.
3,3,5,5-Tetrakis(2-chloro-2-propyl)biphenyl (BPTCC) and 1,3-bis[3,5-bis(2-chloro-2-propyl)phenoxy ]propane (DPPTCC)) was synthesized (Scheme 22) and used as a tetrafunctional initiator for the preparation of 4-arm PIB stars. 81 BPTCC resulted in the synthesis of well-defined products, while DPPTCC gave a mixture of 2-, 3-, and 4-armed stars. This behavior is attributed to the ether bond linking the aliphatic chain and the aromatic ring. These linkages provide significant electron density to the aromatic rings, making them susceptible to Friedel-Crafts cycloaddition reactions following the addition of an isobutene unit to the initiating cation.
3-arm and 4-arm poly(isobutyl vinyl ether) (PIBVE) star homopolymers were synthesized by using trifunctional and tetrafunctional silanol ethers as coupling agents (Scheme 23). The 82 living arms were synthesized at -15 C using the HCl-ZnCl2 initiation system in dichloromethane. The results show that coupling of relatively short living PIBVE chains (DP 10) occurs almost quantitatively, resulting in multi-armed polymers in high yield (95%), but with longer chains, the yield is slightly higher. There was a decline (8589%). Chain of life (DP~50). The final star has a lower molecular weight distribution.