Polyisobutylene (PIB)-based polymer networks potentially useful as smart coatings for photovoltaic devices have been developed. Low molecular weight coumarin functional triarm star PIB was synthesized via a single step SN2 reaction of bromoallyl functional triarm star PIB with 4-methylumbelliferone or umbelliferone in the presence of sodium hydride. Quantitative end functionality was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. UVA (λmax = 365 nm) induced reversible photodimerization of the coumarin moieties resulted in cross-linked elastomeric films exhibiting self-healing behavior. The extent of photodimerization/photoscission was monitored by UV-vis spectroscopy. The low oxygen (1.9 × 10(-16) mol m m(-2) s(-1) Pa(-1)) and moisture (46 × 10(-16) mol m m(-2) s(-1) Pa(-1)) permeability of the cross-linked polymer films suggest excellent barrier properties of the cross-linked polymer films. The self-healing process was studied by atomic force microscopy (AFM). For this, mechanical cuts were introduced in the cross-linked PIB films through micromachining with an AFM tip and the rate of healing induced by UV, sunlight, or both was followed by taking AFM images of the film at different time intervals during the repair process.

A 2 B, and A2B block copolymers, where A ) polyisobutylene, B ) poly-(methyl vinyl ether), and the superscripts denote molecular weight asymmetry, with constant molecular weight and composition have been synthesized by living cationic polymerization. The influence of architecture on aqueous micellar properties of these block copolymers were investigated in the temperature range 20-30 °C by fluorescence spectroscopy and static and dynamic light scattering (SLS and DLS). The critical micelle concentration (cmc) measured at 23 °C increased in the order A 2B < A 1 A 2 B < AB. The partition equilibrium constants, Kv of pyrene, characteristic of hydrophobicity, increased in the opposite order of cmc. The hydrodynamic radii (Rh) and aggregation numbers (Nagg) of micelles remained approximately constant in the whole temperature range for A 1 A 2 B and A2B and below 25 °C for AB. At ∼25 °C, however, there was a sudden increase in both Rh and Nagg for AB. Below 25 °C both Rh and Nagg increased in the order AB < A 1 A 2 B < A2B. The particle size distribution for all block copolymers remained narrow in the whole temperature range. The results are discussed in terms of possible morphologies.

No abstract

No abstract

The anionic ring-opening polymerization of L-lactide was initiated by dipotassium-polyisobutylene-alcoholate telechelic polymer to yield poly(L-lactide)-block-polyisobutylene-block-poly(L-lactide) triblock copolymer, a partially biodegradable thermoplastic elastomer. The pure triblock copolymer was obtained by gradient column chromatography on silica gel. The molar mass and molar mass distribution of the block copolymer was ascertained by SEC and quantitative ' H NMR spectroscopy. It showed two glass transitions and microphase separation.