Precisely Defined Amphiphilic Graft Copolymers

Precise control of grafting density in periodically grafted amphiphilic copolymers: an alternate strategy to fine-tune the lamellar spacing in the sub-10 nm regime

By exactly locating pendant PEG550 segments at varying intervals along a hydrocarbon-rich polyester backbone, the lamellar dimension has been precisely tuned.

De-symmetrizing periodically grafted amphiphilic copolymers: design, synthesis and generation of Janus folded chains

The mutual immiscibility between the three segments, namely backbone HC, and pendant PEG and FC segments, causes zigzag folding of the polymer such that FC segments lie on one side and PEG on the other, thereby generating Janus-type folded chains.

Block co-polyMOFs: morphology control of polymer-MOF hybrid materials

The hybridization of block copolymers and metal-organic frameworks (MOFs) to create novel materials (block co-polyMOFs, BCPMOFs) with controlled morphologies is reported. In this study, block copolymers containing poly(1,4-benzenedicarboxylic acid, H₂bdc) and morphology directing poly(ethylene glycol) (PEG) or poly(cyclooctadiene) (poly(COD)) blocks were synthesized for the preparation of BCPMOFs. Block copolymer architecture and weight fractions were found to have a significant impact on the resulting morphology, mediated through the assembly of polymer precursors prior to MOF formation, as determined through dynamic light scattering. Simple modification of block copolymer weight fraction allowed for tuning of particle size and morphology with either faceted and spherical features. Modification of polymer block architecture represents a simple and powerful method to direct morphology in highly crystalline polyMOF materials. Furthermore, the BCPMOFs could be prepared from both Zr⁴⁺ and Zn²⁺ MOFs, yielding hybrid materials with appreciable surface areas and tuneable porosities. The resulting Zn²⁺ BCPMOF yielded materials with very narrow size distributions and uniform cubic morphologies. The use of topology in BCPMOFs to direct morphology in block copolymer assemblies may open new methodologies to access complex materials far from thermodynamic equilibrium.

Functional α,ω-dienes via thiol-Michael chemistry: synthesis, oxidative protection, acyclic diene metathesis (ADMET) polymerization and radical thiol–ene modification

The synthesis of the novel α,ω-diene 2-(undec-10-en-1-yl)tridec-12-en-1-yl acrylate is described.

Amphiphilic polyethylenes leading to surfactant-free thermoresponsive nanoparticles

Linear copolymers of ethylene and acrylic acid (PEAA) were prepared by catalytic polymerization of ethylene and tert-butyl acrylate followed by hydrolysis of the ester groups. The copolymers contained COOH groups inserted into the crystalline unit cell with formation of intramolecular hydrogen-bonds, as established on the basis of differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) studies. A solvent-exchange protocol, with no added surfactant, converted a solution in tetrahydrofuran of a PEAA sample containing 12 mol % of acrylic acid (AA) into a colloidally stable aqueous suspension of nanoparticles. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and high sensitivity differential scanning calorimetry (HS-DSC) were used to characterize the nanoparticles. They are single crystals of elongated shape with a polar radius of 49 nm (σ = 15 nm) and an equatorial radius of 9 nm (σ = 3 nm) stabilized in aqueous media via carboxylate groups located preferentially on the particle/water interface. The PEAA (AA: 12 mol %) nanoparticles dispersed in aqueous media exhibited a remarkable reversible thermoresponsive behavior upon heating/cooling from 25 to 80 °C.

Model Linear Low Density Polyethylenes from the ROMP of 5-Hexylcyclooct-1-ene

Model hexyl-branched linear low density polyethylene (C8-LLDPE) samples were synthesized by the ring-opening metathesis copolymerization (ROMP) of the 5-hexylcyclooct-1-ene (1) and cyclooctadiene (COD), followed by catalytic hydrogenation. The ROMP of 1 and copolymerization of 1 and COD using the Grubbs second generation catalyst (G2) afford polymers with the number of hexyl branches based on the feed composition. The resulting hexyl-branched polymers, poly(1) and poly(1-stat-COD), were completely converted into model C8-LLDPE samples by catalytic hydrogenation. The C8-LLDPE samples exhibit the expected reduction in density on branching content. The melting temperature (Tm), crystallization temperature (Tc), and heat of fusion/crystallization (ΔHm/ΔHc) of these materials were studied by differential scanning calorimetry.