Amphiphilic tadpole-shaped copolymers consisting of a polystyrene (PS) ring and a poly(ethylene oxide) (PEO) tail were synthesized via atom transfer radical polymerization (ATRP) and click chemistry. First, PEO with a propargyl group and an ATRP initiating group was prepared via click chemistry and esterification. Then, a diblock copolymer, PEO-b-PS, which contained a propargyl group at the junction point and an azide group at the PS chain end, was prepared via ATRP of styrene, followed by transformation of the PS bromo end to an azide group. Finally, cyclization of the PS segment via click chemistry in dilute solution led to the formation of cyclic PS-b-linear PEO (c-PS-b-PEO). Because both the chain length of PEO and the ring size of cyclic PS can be easily tuned, a series of c-PS-b-PEOs was prepared. All of the polymers were characterized with gel permeation chromatography, NMR spectroscopy, FTIR, and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). c-PS-b-PEOs showed smaller hydrodynamic volumes compared with their linear precursors. Self-assembly of one c-PS-b-PEO sample and its linear precursor in water was preliminarily investigated by transmission electron microscopy. We found that vesicles were the main morphologies for both polymers, but they were different in size; those from c-PS-b-PEO were much larger.

The synthesis of a new family of periodic copolymers containing γ-butyrolactones by acyclic diene metathesis polymerization (ADMET) and their thermal properties are presented. Two symmetric diene monomers, M6 and M8, were designed. Both monomers contain two γ-butyrolactone units, but they are different in the length of methylene spacers between cyclic structures and terminal alkenes. The monomers have been prepared by a two-step approach; first, the atom transfer radical addition (ATRA) of diethyl meso-2,5-diiodohexanedioate with either 1,5-hexadiene or 1,7-octadiene was conducted to yield intermediates containing two γ-iodo ester sequences; subsequently, the specific sequence was transformed into γ-butyrolactone unit via intramolecular cyclization upon heating. The two monomers were polymerized using two Grubbs catalysts (Grubbs I and Grubbs II) to produce four polymers with moderate to high molecular weights (P6-1, P6-2, P8-1, and P8-2) and hydrogenation of which gave the final saturated polymers. The expected periodic copolymers have been obtained and were characterized with a variety of methods, indicating that the γ-butyrolactone units could endure the polymerization and hydrogenation. Polymers catalyzed by Grubbs II catalyst suffer from chain heterogeneity due to severe olefin isomerization. Thermal properties of the polymers were investigated via thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA measurements show that these polymers are stable up to 350 °C. DSC results demonstrate that the glass transition and melting behaviors of the polymers are not only affected by the rigidity of γ-butyrolactone units in polyethylene chains but also dependent on the methylene spacer length and chain homogeneity. Copolymerization of M6 or M8 with 1,9-decadiene resulted in random copolymers with lower γ-butyrolactone content and less regular chain structure. These copolymers exhibit lower T g or T m compared with the periodic copolymers.

A new unsymmetrical AB* inimer, p-(2-bromoisobutyloylmethyl)styrene (BiBMS), was applied to the atom transfer radical polymerization (ATRP) to prepare a family of polymers with the topologies ranging from linear to branched. The catalyst system was Cu/CuBr 2 coupled with 2,2 0 -bipyridine (Bipy) or N,N-bis(2pyridylmethyl)octylamine (BPMOA) as a ligand in toluene or anisole at different temperatures, which ensured a very low catalyst (CuBr) concentration throughout the polymerization by a slow reduction process. First, BiBMS was polymerized in anisole at 0 °C using Cu/CuBr 2 /BPMOA as a catalyst system; at this temperature, the initiating activity of the formed A* was frozen and the polymerization was a step-growth polymerization, resulting in the formation of a linear polymer (LP1) whose main chain was linked by ester bonds. Second, BiBMS was polymerized in toluene at 20 °C using Cu/CuBr 2 /Bipy as a catalyst system. Under this condition, initiation from the B* of BiBMS was slow, followed by a fast radical polymerization of the BiBMS vinyl bonds and a slow deactivation, thereby affording another linear polymer (LP2), the structure of which was the same as that obtained by common free radical polymerization of BiBMS except the end groups. The conversion of BiBMS was controlled to be moderate to suppress the possible initiation from the pendant B* along the polymer main chain. Third, BiBMS was polymerized in anisole at various temperatures using Cu/CuBr 2 /Bipy as a catalyst system; three branched polymers (BP1, BP2, BP3) with different degree of branching (DB) were obtained, the DB of which could be easily adjusted by changing temperature (BP1, DB = 0.12 at 20 °C; BP2, DB = 0.26 at 40 °C; BP3, DB = 0.37 at 60 °C).