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The formation of block copolymer nanoparticles is commonly obtained by switching solvent quality from good solvent for both blocks to a selective solvent for one block. The effect of the selective solvent on particle dimension, shape and inner structure has been analyzed in detail, instead less attention has been focused on the role of the common solvent. Poly(ethylene oxide)- block -poly(lactic acid) (PEO- b -PLA) is widely used for the preparation of nanometric drug delivery systems and the control of the particle morphology has relevant effects on bioactivity. In this work we investigate the effect of using different common solvents (acetone, dioxane, tetrahydrofuran, dimethylformamide) on the self-assembly behavior of narrowly dispersed PEO- b -PLA copolymers, synthesized by metal free ring-opening polymerization, with large variation of molecular weight of the hydrophobic block (from 65 to 1300 lactic units). Dynamic light scattering (DLS) and cryo-electron microscopy (cryo-EM) analyses of PEO- b -PLA nanoparticles reveal that their size and shape are strongly dependent on the hydrogen bonding ability of the common solvent used in the self-assembly process. As consequence of these variations, also the cytoxicity of the nanoparticles is affected. Image 1 • A library of PEO- b -PLA copolymers has been synthesized by DBU catalyzed ROP. • The self-assembly of PEO- b -PLA copolymers has been realized in a variety of common solvents. • The hydrogen bonding ability of the solvent has a relevant effect on the self-assembly. [ABSTRACT FROM AUTHOR]

Different strategies of inclusion were employed to obtain mesoporous channel-like silica MCM-41 with different content of terthiophene (3T), from almost isolated molecules to nearly filled nanochannels, and studied by optical measurements. In the first case, photoluminescence spectra of inclusion compounds were similar to dilute solution 3T emission, demonstrating the dispersive role of the silica matrix. In the second case, emission spectra resemble that of 3T crystals revealing the presence of an organic nanophase within the nanochannels. Simple estimations of the size of these nanoaggregates suggest that few tens of molecules are sufficient to give rise to bulk optical properties. [Copyright &y& Elsevier]

Diels-Alder chemistry has been used for the thermoreversible cross-linking of furan-functionalized ethylene/propylene (EPM) and ethylene/vinyl acetate (EVM) rubbers. Both furan-functionalized elastomers were successfully cross-linked with bismaleimide to yield products with a similar cross-link density. NMR relaxometry and SAXS measurements both show that the apolar EPM-g-furan precursor contains phase-separated polar clusters and that cross-linking with polar bismaleimide occurs in these clusters. The heterogeneously cross-linked network of EPM-g-furan contrasts with the homogeneous network in the polar EVM-g-furan. The heterogeneous character of the cross-links in EPM-g-furan results in a relatively high Young's modulus, whereas the more uniform cross-linking in EVM-g-furan results in a higher tensile strength and elongation at break. [ABSTRACT FROM AUTHOR]

Chain-dynamics of flexible synthetic macromolecules in the crystalline state has been clarified by multinuclear solid-state NMR observations. Massive motional phenomena are shown when chains are crystallized in the hexagonal phase. Several examples have been surveyed, where motion is induced by high temperature and pressure or favored by inclusion of moderate amounts of comonomer units in the main chain and by the use of monomers containing mobile side chains. Also, motional phenomena of fast spinning and large librations of the macromolecules are promoted when the isolated chains are confined to nanochannels formed in hexagonal crystal structures of suitable matrices. The motional behavior can be modulated by the topology and the interactions in the unusual environments. This knowledge provides information about polymers in close contact with heterogeneous interfaces, such as polymers in nanocomposites or at surfaces. [ABSTRACT FROM AUTHOR]