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Blending with a homopolymer is an effective approach to tailor the microphase-separated morphology of block copolymers. It has been established for the blends of coil–coil diblock copolymer (A-b-B) with the corresponding homopolymer (h-A) that h-A can be solubilized uniformly into A mcirodomain to induce structure transformation when its molecular weight is smaller than that of the A block, i.e., α = Mh-A/Mb-A < 1. Here we examine if the microdomain structure of a rod–coil diblock copolymer, poly(2,5-diethylhexyloxy-1,4-phenylenevinylene)-block-poly(methyl methacrylate) (DEH-PPV-b-PMMA), may be systematically tuned by blending with PMMA hompolymer (h-PMMA). The blends over the major composition window were found to undergo macrophase separation even when the value of α was as low as 0.3. The phase separation led to the formation of a copolymer-rich phase and a homopolymer-rich phase, in which microphase separation occurred, yielding a well-ordered lamellar structure and a sponge structure, respectively. T...

While ordered bicontinuous double diamond (OBDD) in block copolymers has always been considered as an unstable structure relative to ordered bicontinuous double gyroid (OBDG), here we report the existence of a thermodynamically stable OBDD structure in a diblock copolymer composed of a stereoregular block. A slightly asymmetric syndiotactic polypropylene-block-polystyrene (sPP-b-PS) as cast from xylene was found to display the OBDD morphology. When the OBDD-forming diblock was heated, this structure transformed to the OBDG phase at ca. 155 °C. Interestingly, OBDD was recovered upon cooling even in the temperature range above melting point of sPP, indicating that OBDD was a thermodynamically stable structure for sPP-b-PS melt, which was in contradiction to the conventional view. We propose that the larger free energy cost encountered in OBDD due to the larger packing frustration may be compensated sufficiently by the release of free energy due to local packing of the conformationally ordered segments of sP...

All conjugated C60-containing block copolymers (BCPs) based on quasi-living Grignard metathesis (GRIM) polymerization have been designed and synthesized for application in polymer solar cells (PSCs). The C60-containing BCP can induce the formation of a self-organization nanostructure of P3HT domain. Moreover, this C60-containing BCP serves as a compatibilizer to reduce the interfacial tension between the P3HT and C60, thus help establishing a moderate phase-separated morphology with crystalline P3HT and C60 domain. The performance up to 2.56%(AM 1.5G irradiation (100 mW/cm2)) of a P3HT:C60 device can be achieved by using C60–BCP as additive without any post-treatment.

We prepared aligned poly(3-hexylthiophene) (P3HT) nanofibers for the application of organic field-effect transistor (OFET) by two-fluid coaxial electrospinning (ES) technique using P3HT as core and PMMA as shell, followed by extraction of PMMA. Effects of shell flow rate and thermal annealing temperature on the morphology and optoelectronic properties were explored. The experimental results showed that the prepared P3HT nanofibers were highly aligned and their diameters were smaller in the case of low shell flow rate. The OFET carrier mobility of aligned P3HT ES nanofibers using the low shell flow rate could be dramatically improved up to 3 orders of magnitude (1.92 × 10−1 cm2/V·s with the on/off ratio of 4.45 × 104) in comparison with those from the high shell flow rate. The results of wide-angle X-ray scattering (WAXS) and photophysical properties (optical absorption and polarized photoluminescence) suggested the enhancement of π−π stacking and crystallinity of P3HT in the nanofibers at a lower shell fl...

The structures of an amphiphilic conjugated graft copolymer, poly(2,3-diphenyl-5-(trimethylene-heptadeca(oxyethylene)-methoxy-phenylene vinylene) (denoted as PVEO17) composing of a conjugated DPPPV backbone and PEO side chains, in bulk and solutions with tetrahydrofuran (THF) and water have been investigated by small-angle X-ray scattering (SAXS). In bulk state, the DP-PPV main chains in PVEO17 stacked to form flat disk microdomains dispersed in the PEO side-chain matrix. The corresponding wide angle X-ray scattering pattern revealed the existence of crystallinity of the PEO side chains. The structure of the polymer in solution was affected by the solvent quality and the polymer concentration. PVEO17 chains were relatively well dispersed in THF. In aqueous solutions, however, the amphiphilic PVEO17 chains aggregated significantly over the concentration range of 1–8 wt%, where the polymer was found to self-organize to form cylindrical micelles with the aggregation number increasing with the increase of concentration. The photophysical properties characterized by UV–Vis and photoluminescence spectroscopy were strongly affected by the aggregation state of the polymer.

Functional poly(carbonate-b-ester)s were synthesized in buck by ring-opening polymerization of the carbonate (TMC, MBC, or BMC) with tert-butyl N-(2-hydroxyethyl) carbamate as an initiator, and then with e-CL (or e-BCL) comonomer. Subsequently, the PMMC-b-PCL with pendent carboxyl groups and the PTMC-b-PHCL with pendent hydroxyl groups were obtained by catalytic debenzylation. DSC analysis indicated that only one Tg at an intermediate temperature the Tgs of the two polymer blocks. A decrease Tg was observed when an increase contents of e-CL incorporated into the copolymers. In contrast, two increased Tms were observed with increasing PCL content. The block copolymers formed micelle in aqueous phase with critical micelle concentrations (cmcs) in the range of 2.23–14.6 mg/L and with the mean hydrodynamic diameters in the range of 100–280 nm, depending on the composition of copolymers. The drug entrapment efficiency and hydrolytic degradation behavior of micelle were also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

We report the synthesis and the self-assembled morphologies of a series of new rod-coil diblock copolymers, poly[2,7-(9,9-dihexylfluorene)]-b-poly(4-vinylpyridine) (PF-b-P4VP). The rod-coil diblock copolymers were synthesized via Suzuki coupling reaction and living anionic polymerization. Probing by transmission electron microscopy, small-angle X-ray scattering and atomic force microscopy, we found that the microphase separation varies from lamellar to cylindrical and then to spherical, depending on the length of P4VP blocks. The P4VP coil blocks were further hydrogen-bonded with 3-pentadecylphenol (PDP) to form rod-comb block copolymers. Similar to conventional coil-coil block copolymers-based supramolecules, the incorporation of PDP transforms the morphologies from lamellar to cylindrical or from cylindrical to spherical due to the increase of volume fraction of P4VP(PDP) comb blocks. The strategy described here can be used to tune the self-assembled structures of rod-coil block copolymers.