Topology Effect on Order-Disorder Transition of High-χ Block Copolymers.

This work aims to systematically examine the topology effect on the self-assembly of block copolymers. Compositionally, symmetric polystyrene--polydimethylsiloxane block copolymers (BCPs) with different chain topologies (diblock, three-arm star-block, and four-arm star-block) and various molecular weights are synthesized. These purposely designed block copolymers are used as a model system to investigate the topology effect on order-to-disorder transition temperature ( ) by temperature-resolved small-angle X-ray scattering experiments.

Frank-Kasper-like network phase from self-assembly of high-χ star-block copolymers.

By taking advantage of the effects of solvent selectivity and topology on high-χ block copolymer (BCP) for self-assembly, network phases with high packing frustration can be formed in self-assembled polystyrene--polydimethylsiloxane (PS--PDMS). Apart from gyroid with trigonal structure and diamond with tetrahedral structure, a peculiar network phase with space group of [Formula: see text] (Frank-Kasper structure) can be found in six-arm star-block PS--PDMS as evidenced by small-angle x-ray scattering. Electron tomography results reveal the network phase with alternating connection of three and four struts.

Synthesis and Structural Insight into poly(dimethylsiloxane)--poly(2-vinylpyridine) Copolymers.

In this study, the use of anionic polymerization for the synthesis of living poly(dimethylsiloxane) or PDMS-Li, as well as poly(2-vinylpyridine) or P2VP-Li homopolymers, and the subsequent use of chlorosilane chemistry in order for the two blocks to be covalently joined leading to PDMS--P2VP copolymers is proposed. High vacuum manipulations enabled the synthesis of well-defined materials with different molecular weights (Μ¯n, from 9.8 to 36.

Thermal and Bulk Properties of Triblock Terpolymers and Modified Derivatives towards Novel Polymer Brushes.

We report the synthesis of three (3) linear triblock terpolymers, two (2) of the ABC type and one (1) of the BAC type, where A, B and C correspond to three chemically incompatible blocks such as polystyrene (PS), poly(butadiene) of exclusively (~100% vinyl-type) -1,2 microstructure (PB) and poly(dimethylsiloxane) (PDMS) respectively. Living anionic polymerization enabled the synthesis of narrowly dispersed terpolymers with low average molecular weights and different composition ratios, as verified by multiple molecular characterization techniques. To evaluate their self-assembly behavior, transmission electron microscopy and small-angle X-ray scattering experiments were conducted, indicating the effect of asymmetric compositions and interactions as well as inversed segment sequence on the adopted morphologies.

Synthesis and Characterization of Hybrid Materials Derived from Conjugated Copolymers and Reduced Graphene Oxide.

In this study the preparation of hybrid materials based on reduced graphene oxide (rGO) and conjugated copolymers is reported. By tuning the number and arrangement of thiophenes in the main chain (indacenothiophene or indacenothienothiophene) and the nature of the polymer acceptor (difluoro benzothiadiazole or diketopyrrolopyrrole) semiconducting copolymers were synthesized through Stille aromatic coupling and characterized to determine their molecular characteristics. The graphene oxide was synthesized using the Staudenmaier method and was further modified to reduced graphene oxide prior to structural characterization.

Vacuum-Driven Orientation of Nanostructured Diblock Copolymer Thin Films.

This work aims to demonstrate a facile method for the controlled orientation of nanostructures of block copolymer (BCP) thin films. A simple diblock copolymer system, polystyrene--polydimethylsiloxane (PS--PDMS), is chosen to demonstrate vacuum-driven orientation for solving the notorious low-surface-energy problem of silicon-based BCP nanopatterning. By taking advantage of the pressure dependence of the surface tension of polymeric materials, a neutral air surface for the PS--PDMS thin film can be formed under a high vacuum degree (∼10 Pa), allowing the formation of the film-spanning perpendicular cylinders and lamellae upon thermal annealing.

Block Copolymer Modified Nanonetwork Epoxy Resin for Superior Energy Dissipation.

Herein, this work aims to fabricate well-ordered nanonetwork epoxy resin modified with poly(butyl acrylate)--poly(methyl methacrylate) (PBA--PMMA) block copolymer (BCP) for enhanced energy dissipation using a self-assembled diblock copolymer of polystyrene--poly(dimethylsiloxane) (PS--PDMS) with gyroid and diamond structures as templates. A systematic study of mechanical properties using nanoindentation of epoxy resin with gyroid- and diamond-structures after modification revealed significant enhancement in energy dissipation, with the values of 0.36 ± 0.

Molecular and Structure-Properties Comparison of an Anionically Synthesized Diblock Copolymer of the PS--PI Sequence and Its Hydrogenated or Sulfonated Derivatives.

An approach to obtaining various nanostructures utilizing a well-studied polystyrene--poly(isoprene) or PS--PI diblock copolymer system through chemical modification reactions is reported. The complete hydrogenation and partial sulfonation to the susceptible carbon double bonds of the PI segment led to the preparation of [polystyrene--poly(ethylene--propylene)] as well as [polystyrene--poly(sulfonated isoprene--isoprene)], respectively. The hydrogenation of the polyisoprene block results in enhanced segmental immiscibility, whereas the relative sulfonation induces an amphiphilic character in the final modified material.

Synthesis, Characterization and Structure Properties of Biobased Hybrid Copolymers Consisting of Polydiene and Polypeptide Segments.

Novel hybrid materials of the PB--P(o-Bn-L-Tyr) and PI--P(o-Bn-L-Tyr) type (where PB: 1,4/1,2-poly(butadiene), PI: 3,4/1,2/1,4-poly(isoprene) and P(o-Bn-L-Tyr): poly(ortho-benzyl-L-tyrosine)) were synthesized through anionic and ring-opening polymerization under high-vacuum techniques. All final materials were molecularly characterized through infrared spectroscopy (IR) and proton and carbon nuclear magnetic resonance (H-NMR, C-NMR) in order to confirm the successful synthesis and the polydiene microstructure content. The stereochemical behavior of secondary structures (α-helices and β-sheets) of the polypeptide segments combined with the different polydiene microstructures was also studied.

Structure/Properties Relationship of Anionically Synthesized Diblock Copolymers "" Chemically Modified Graphene.

A novel approach to obtaining nanocomposite materials using anionic sequential polymerization and post-synthetic esterification reactions with chemically modified graphene sheets (CMGs) is reported. The anionically synthesized diblock copolymer precursors of the PS--PI-OH type were grafted to the chemically modified -COOH groups of the CMGs, giving rise to the final composite materials, namely polystyrene--poly(isoprene)--CMGs, which exhibited enhanced physicochemical properties. The successful synthesis was determined through multiple molecular characterization techniques together with thermogravimetric analysis for the verification of increased thermal stability, and the structure/properties relationship was justified through transmission electron microscopy.

Mesoscale networks and corresponding transitions from self-assembly of block copolymers.

A series of cubic network phases was obtained from the self-assembly of a single-composition lamellae (L)-forming block copolymer (BCP) polystyrene-block-polydimethylsiloxane (PS--PDMS) through solution casting using a PS-selective solvent. An unusual network phase in diblock copolymers, double-primitive phase (DP) with space group of [Formula: see text], can be observed. With the reduction of solvent evaporation rate for solution casting, a double-diamond phase (DD) with space group of [Formula: see text] can be formed.

Dendrons and Dendritic Terpolymers: Synthesis, Characterization and Self-Assembly Comparison.

To the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved.

Self-Assembly of Low-Molecular-Weight Asymmetric Linear Triblock Terpolymers: How Low Can We Go?

The synthesis of two (2) novel triblock terpolymers of the ABC type and one (1) of the BAC type, where A, B and C are chemically different segments, such as polystyrene (PS), poly(butadiene) (PB) and poly(dimethylsiloxane) (PDMS), is reported; moreover, their corresponding molecular and bulk characterizations were performed. Very low dimensions are evident from the characterization in bulk from transmission electron microscopy studies, verified by small-angle X-ray data, since sub-16 nm domains are evident in all three cases. The self-assembly results justify the assumptions that the high Flory-Huggins parameter, , even in low molecular weights, leads to significantly well-ordered structures, despite the complexity of the systems studied.

Alternating Gyroid Network Structure in an ABC Miktoarm Terpolymer Comprised of Polystyrene and Two Polydienes.

The synthesis, molecular and morphological characterization of a 3-miktoarm star terpolymer of polystyrene (PS, M¯n = 61.0 kg/mol), polybutadiene (PB, M¯n = 38.2 kg/mol) and polyisoprene (PI, M¯n = 29.