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The phase behavior of block copolymers (BCPs) at the water‐oil interface is influenced by the segmental interaction parameter (χ ${\chi }$) and chain architecture. We synthesized a series of star block copolymers (s‐BCPs) having polystyrene (PS) as core and poly(2‐vinylpyridine) (P2VP) as corona. The interaction parameters of block‐block (χ ${\chi }$ PS‐P2VP) and block‐solvent (χ ${\chi }$ P2VP‐solvent) were varied by adjusting the pH of the aqueous solution. Lowering pH increased the fraction of quaternized‐P2VP (Q‐P2VP) with enhanced hydrophilicity. By transferring the equilibrated interfacial assemblies, morphologies ranging from bicontinuous films at pH of 7 and 3.1 to nanoporous and nanotubular structure at pH of 0.65 were observed. The nanoporous films formed hexagonally packed pores in s‐BCP matrix, while nanotubes comprised Q‐P2VP as corona and PS as core. Control over pore size, d‐spacing between pores, and nanotube diameters was achieved by varying polymer concentration, molecular weight, volume fraction and arm number of s‐BCPs. Large‐scale nanoporous films were obtained by freeze‐drying emulsions. Remarkably, the morphologies of linear BCPs were inverted, forming hexagonal‐packed rigid spherical micelles with Q‐P2VP as core and PS as corona in multilayer. This work provides insights of phase behaviors of BCP at fluids interface and offer a facile approach to prepare nanoporous film with well‐controlled pore structure. [ABSTRACT FROM AUTHOR]

A systematic comparison between graft poly( l-lactide) copolymers with different topologies and their ability to form stereocomplexes with poly( D-lactide) (PDLA) is performed. Comb and hyperbranched copolymers based on functional poly(ethylene glycol) and poly( l-lactide) with molecular weights in the range of 2000-90 000 g mol−1 and moderate molecular weight distributions ( Mw/ Mn = 1.08-1.37) are prepared via the combination of anionic and ring-opening polymerization. Two 'topological isomers,' a linear poly(ethylene oxide)/poly(glycerol) (PEG/PG) copolymer and a branched PEG/PG copolymer are used as backbone polymers. Furthermore, the stereocomplex formation between PDLA and the hyperbranched and comb copolymers containing poly( l-lactide) arms is studied. Stereocomplex formation is confirmed by DSC as well as by Fourier transform IR (FTIR) and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Imino- and amino-pyridine ligands are versatile scaffolds to probe how ligand sterics influence polymerization outcomes for nickel(II) ethylene polymerization catalysts. Six imino- and one amino-pyridine nickel(II) complexes with varied imino/amino-carbon substitution (R 1  = methyl, ethyl, isopropyl or tert -butyl) were synthesized ( 1 - 7 ). Five of these complexes were analyzed crystallographically: dimeric {[2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 } 2 (R 1  = Et 2 ; R 1  =  t -Bu 4 ), monomeric [2-[(2,6-Me 2 -C 6 H 3 )N=C(R 1 )]C 5 H 4 N]NiBr 2 NCCH 3 (R 1  = Me 5 ; R 1  =  t -Bu 6 ), and monomeric [2-[(2,6-Me 2 -C 6 H 3 )NHCH( t -Bu)]C 5 H 4 N]NiBr 2 ( 7 ). Complexes 1 - 7 are competent ethylene polymerization precatalysts at 0 ° C, and tert -butyl substituted imino-pyridine precatalysts 4 and 6 and amino-pyridine precatalyst 7 display the best activity, highest polyethylene molecular weight, and narrowest dispersity values of series. 13 C-NMR analyses of polyethylene samples reveal a lightly branched morphology with a modest amount of methyl branching; polymer T m values are consistent with this assessment. Ongoing work includes further exploration of precatalysts 4 , 6 , and 7 in attempt to maximize polyethylene molecular weight and achieve living polymerization. [ABSTRACT FROM AUTHOR]

Amphiphilic cationic polynorbomene derivatives, soluble in water, were prepared from modular norbornene monomers, with a wide range of molecular weights (Mn = 1600-137 500 g/mol) and narrow polydispersities (PDl = 1.1-1.3). The antibacterial activity determined by growth inhibition assays and the hemolytic activity against human red blood cells were measured and compared to determine the selectivity of the polymers for bacterial over mammalian cells. The effects of monomer repeat unit hydrophobicity and polymer molecular weight on antibacterial and hemolytic activities were determined. The hydrophobicity of the repeat unit was observed to have dramatic effects on antibacterial and hemolytic activities. Lipid membrane disruption activities of the polymers was confirmed by measuring polymer-induced dye leakage from large unilamellar vesicles. By tuning the overall hydrophobicity of the polymer through random copolymerizations of modular norbornene derivatives, highly selective, nonhemolytic antibacterial activities were obtained. For appropriate monomer composition, selectivity against bacteria versus human red blood cells was determined to be over 100. [ABSTRACT FROM AUTHOR]