The synthesis of well-defined graft copolymers of poly(γ-benzyl-L-glutamate)-g-polytetrahydrofuran, PBLG-g-PTHF, has been achieved via controlled termination of living PTHF branch chains with −NH− functional groups along PBLG macromolecular backbone. The PBLG backbone with different molecular weights (M n = 2000−45000 g·mol −1 ) were prepared by anionic ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydrade (BLG-NCA). Living PTHF chains with predictable chain length (M n = 720−7000 g·mol −1 ) were prepared by living cationic ring-opening polymerization of THF with methyl triflate (MeOTf) as an initiator. The grafting efficiency (G E ) of living PTHF chains onto PBLG backbone via controlled termination reached to near 100%. The grafting density (G D ) along PBLG backbone and average number of PTHF branches (N b,PTHF ) in PBLG-g-PTHF graft copolymers could be mediated by changing the molar ratio of living PTHF chains to −NH− functional groups. Circular dichroism (CD) and FTIR spectra show that some of the graft copolymers maintain α-helical structure from PBLG, and the strength of CD signals for α-helical structure of the graft copolymers also decreased with increasing G D . The crystallization degree and spherulitic growth rate of the PBLG-g-PTHF graft copolymers decreased with increasing G D . The obvious phase separation and reticular state of aggregation morphology in PBLG-g-PTHF graft copolymers could be observed. PBLG-g-PTHF graft copolymers have no cytotoxicity and even conducive for cell survival. These graft copolymers had extremely low bibulous rate, and all the water absorption ratios were kept around 1.02 to maintain the shape and dimensional stability.

a 5,6-Diboromo-1,10-phenanthroline and 2,9-di-n-butyl-5,6-dibromo-1,10-phenanthroline were polymerized using a Ni catalyst to afford helical polymers in which the phenanthroline moieties are densely stacked on top of each other. Polymerization of the latter monomer using a chiral catalyst led to a preferredhanded helix. This is the first Ni-catalyzed helix-sense-selective polymerization of aromatic compound.Helical polymers are an important class of material that finds a wide range of applications such as chiral recognition, nonlinear optics, and chiral catalysis.1 Such a conformation has been realized for various types of synthetic polymers including vinyl polymers, conjugated polymers and polymers containing hetero atoms in the main chain. 2 Among main-chain conjugated polymers, poly(ophenylene) and its derivatives may be expected to form a helical conformation due to restricted rotation around single bonds connecting aromatic groups arising from steric hindrance and π-stacking between aromatic groups. However, examples of synthesis and structural analysis of poly(o-phenylene) and its derivatives are far more limited compared with poly(para-phenylene) and its derivatives. The first synthesis of poly(o-phenylene) was attempted by Wittig 3 through coupling of o-dilithiobenzene in the presence of transition metal salt resulting in products that seem to be cyclic compounds. Later, Ullmann reaction 4 , Kumada coupling 5 and electrochemical polymerization 6 aiming at poly(o-phenylene) were also reported. Conventional step-by-step methods such as Suzuki coupling 7 and copper-mediated oxidative coupling 8 were also used.Recently, polymerizations of aryne and oxabicyclic alkene with copper and palladium catalysis, respectively, were developed. 9 As one of the most noticeable achievements, uniform poly(ophenylene) derivatives up to 48-mer were synthesized through copper-mediated oxidative reaction of lithiated precursors starting from a 2,2'-biphenyl derivative and n-BuLi, and a tight helical conformation was clarified through X-ray crystal analysis. 8 In this case, single-handed helix was obtained through resolution by triage of conglomerate crystals 8a as well as chiral HPLC.

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