Effect of Hydrophilic Monomer Distribution on Self-Assembly of a pH-Responsive Copolymer: Spheres, Worms and Vesicles from a Single Copolymer Composition.

A series of copolymers containing 50 mol % acrylic acid (AA) and 50 mol % butyl acrylate (BA) but with differing composition profiles ranging from an AA-BA diblock copolymer to a linear gradient poly(AA-grad-BA) copolymer were synthesized and their pH-responsive self-assembly behavior was investigated. While assemblies of the AA-BA diblock copolymer were kinetically frozen, the gradient-like compositions underwent reversible changes in size and morphology in response to changes in pH. In particular, a diblock copolymer consisting of two random copolymer segments of equal length (16 mol % and 84 mol % AA content, respectively) formed spherical micelles at pH >5, a mix of spherical and wormlike micelles at pH 5 and vesicles at pH 4. These assemblies were characterized by dynamic light scattering, cryo-transmission electron microscopy and small angle neutron scattering.

Organocatalytic Michael Addition as a Method for Polyisobutylene Chain-End Functionalization.

Functionalization of polyolefins, in particular polyisobutylene, remains a relatively unexplored application for the Michael reaction. This work evaluates the potential of polyisobutylene acrylate (PIBA) chain-end modification via organocatalyzed thiol-Michael and aza-Michael additions. A series of chain-end functional polyisobutylene oligomers are prepared using "click" reactions of thiols or amines to PIBA in the presence of 0.02 equivalents of organocatalyst. Reaction kinetics and chain-end transformations are monitored using NMR spectroscopy and the macromolecular products are characterized by size exclusion chromatography. Further potential of this synthetic strategy is illustrated by thiol-Michael addition of thiols formed in situ via nucleophilic thiolactone ring opening. The obtained results provide an efficient method for the preparation of functional polyisobutylene oligomers that can be utilized in a broad range of potential applications.

Alkyl Triarylstannanecarbodithioates: Synthesis, Crystal Structures, and Efficiency in RAFT Polymerization.

Eight alkyl triarylstannanecarbodithioates were synthesized starting from the corresponding triarylstannyl chlorides. They were fully characterized by IR and 1 H, 13 C, and 119 Sn NMR spectroscopy and mass spectrometry. Their solid-state structures and geometric parameters were determined and compared to those of other classes of thiocarbonylthio compounds. These new organotin derivatives are efficient reversible chain-transfer agents for reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St) and n-butyl acrylate (BA), with controlled number-average molecular weights and narrow dispersities (Ð<1.3). In some cases, loss of control of the polymerization was evidenced and supported by the observation of side products by 119 Sn NMR spectroscopy. This phenomenon was attributed to the thermal instability of the Sn-RAFT terminal group.

Phosphinoyl and thiophosphinoylcarbodithioates: synthesis, molecular structure, and application as new efficient mediators for RAFT polymerization.

New phosphinoyl and thiophosphinoylcarbodithioates were synthesized in a one-pot reaction from the corresponding phosphinochalcogenides. Compounds of this new generation of thiocarbonylthio derivatives have been fully characterized by IR as well as (1)H, (31)P, and (13)C NMR spectroscopy and by mass spectrometry. Their solid-state structures reveal that they are isostructural but crystallize in different space groups. These new compounds are highly efficient reversible chain-transfer agents for the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St) and n-butyl acrylate (nBA), with controlled number-average molecular weights (Mn) and narrow dispersity values (Ð<1.3). The controlled character of the polymerization was further exemplified by MALDI-TOF mass spectrometry and the synthesis of PSt-P(nBA) diblock copolymers.

Quench ionic flash nano precipitation as a simple and tunable approach to decouple growth and functionalization for the one-step synthesis of functional LnPO4-based nanoparticles in water.

A novel, one-step method for the synthesis of functional, organic-inorganic hybrid nanoparticles is reported. The quench ionic Flash NanoPrecipitation (qiFNP) method enables the straightforward synthesis of nanoparticles by decoupling the formation of the inorganic core and surface functionalization. As a proof-of-concept, the qiFNP method was successfully applied for the tunable and highly controlled synthesis of various LnPO4-based nanomaterials for bioimaging applications.

RAFT Polymerization with Triphenylstannylcarbodithioates (Sn-RAFT).

A new range of tin-based reversible addition-fragmentation chain-transfer (RAFT) agents is described and evaluated for the polymerization of acrylamides, methyl acrylate and styrene. These organometallic compounds are highly reactive reversible transfer agents which allow an efficient control of the polymerization of substituted acrylamide monomers, whereas RAFT control for methyl acrylate and styrene polymerization is contaminated by side reactions at prolonged reaction times. 119Sn NMR is shown to be an informative instrument for the monitoring of Sn-RAFT-mediated polymerizations.