Autonomous motility of polymer films coupled to stimuli gradients

Adaptive soft materials exhibit a diverse set of behaviors including reconfiguration, actuation, and locomotion. These responses are typically optimized in isolation. Here, we explore the interrelation between these behaviors by developing a behavioral phase diagram for hygromorphic polymer films. We determine that the dynamic behaviors are a result of not only a response to, but also an interaction with a humidity gradient, which can be tuned via control of the environment and film characteristics, including size, permeability and coefficient of hygroscopic expansion to target a desired behavior such as multi-modal locomotion. Using the improved understanding of stimuli interactive materials gained from our study of monolithic polymer films, we demonstrate how robust composites can be designed to exhibit autonomous, environmentally-responsive behaviors, and how these concepts can be incorporated into origami structures to engineer the extent and sequence of motions

Synthesis of Photoresponsive Dual NIR Two-Photon Absorptive [60]Fullerene Triads and Tetrads

Broadband nonlinear optical (NLO) organic nanostructures exhibiting both ultrafast photoresponse and a large cross-section of two-photon absorption throughout a wide NIR spectrum may make them suitable for use as nonlinear biophotonic materials. We report here the synthesis and characterization of two C60-(antenna)x analogous compounds as branched triad C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2 nanostructures. These compounds showed approximately equal extinction coefficients of optical absorption over 400–550 nm that corresponds to near-IR two-photon based excitation wavelengths at 780–1,100 nm. Accordingly, they may be utilized as potential precursor candidates to the active-core structures of photosensitizing nanodrugs for 2γ-PDT in the biological optical window of 800–1,050 nm.United States. Air Force Office of Scientific Research (grant number FA9550-09-1-0380)United States. Air Force Office of Scientific Research (Grant FA9550-09-1-0183)National Institutes of Health (U.S.) (grant number 4R01CA137108)National Institutes of Health (U.S.) (NIH R01AI058075

Structural systematics in isomorphous binary cocrystal solvates comprising 2,2′-dithiodibenzoic acid, 4-halobenzoic acid and dimethylformamide (1 : 1 : 1), for halide = chloride, bromide and iodide

The 1:1:1 binary co-crystal solvates formulated as 2,2'-dithiodibenzoic acid (DTBA), 4-halobenzoic acid (4-XBA) and dimethylformamide (DMF) for X = Cl (1), Br (2) and I (3) are isomorphous and the supramolecular association in this series has been probed by a wide range of computational chemistry techniques. The common feature of the molecular packing is the formation of robust three-molecule aggregates sustained by a non-symmetric {···HOC=O}2 synthon, formed between DTBA and 4-XBA, and a DTBA-hydroxyl-O–H···O(carbonylDMF) hydrogen bond (with a reciprocating DMF-C–H···O(carbonyl-DTBA) contact). Supramolecular tapes are evident and feature DTBA-C–H···O(DMF), DTBA-C–H···S(DTBA), DMF-O···π(DTBA-phenyl) and DMF-C–H···π(DTBA-phenyl) contacts. The point-to-point connections between tapes are of the type π(4-XBA-phenyl)···π(DTBA-phenyl), π(4-XBA-phenyl)···π(4-XBA-phenyl), DTBA-C–H···π(DTBA-phenyl) and DMF-C···

Grafting of 4-(2,4,6-Trimethylphenoxy)benzoyl onto Single-Walled Carbon Nanotubes in Poly(phosphoric acid) via Amide Function

Single-walled carbon nanotubes (SWCNTs), which were commercial grade containing 60–70 wt% impurity, were treated in a mild poly(phosphoric acid) (PPA). The purity of PPA treated SWCNTs was greatly improved with or without little damage to SWCNTs framework and stable crystalline carbon particles. An amide model compound, 4-(2,4,6-trimethylphenoxy)benzamide (TMPBA), was reacted with SWCNTs in PPA with additional phosphorous pentoxide as “direct” Friedel–Crafts acylation reaction to afford TMPBA functionalized SWCNTs. All evidences obtained from Fourier-transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, scanning electron microcopy, and transmission electron microscopy strongly supported that the functionalization of SWCNTs with benzamide was indeed feasible

Macromolecular dumbbells: synthesis and photophysical properties of hyperbranched poly(etherketone)-b-polybenzobisthiazole-b-hyperbranched poly(etherketone) ABA triblock copolymers

A series of hyperbranched poly(etherketone)-b-poly(benzobisthiazole)-b-hyperbranched poly(etherketone) triblock copolymers were synthesized. Two different types of hyperbranched poly(etherketone)s (PEKs) were utilized as dendritic A-block units and carboxylic acid-terminated polybenzobisthiazoles (PBZTs) with two different molecular weights as a conjugated, optically responsive, rigid-rod B-block units to afford dumbbell-shaped ABA triblock copolymers. Although all dumbbell-shaped samples are soluble in strong acids such as trifluoroacetic acid (TFA), methanesulfonic acid (MSA), trifluoromethanesulfonic acid (TFMSA) and sulfuric acid, only phenoxy-terminated dumbbell shaped triblock copolymers (3a and 3b) were soluble in common polar aprotic solvents such as NMP, DMF, DMAc and DMSO. Their solubility in common organic solvents was apparently a consequence arising from the obstruction of the close packing of PBZT components by the bulky dendritic PEK ends. A very surprising and interesting observation was made when the 3a and 3b solutions in NMP were placed under room light for 24 h: all major absorption peaks became featureless and blue-shifted. This photochromism was investigated by static and dynamic UV-absorption and fluorescence spectroscopy under various conditions. Although the response time was quite long, it could be controlled as a function of excitation wavelength, light intensity, and solvent viscosity and/or polarity. We propose that the origin of observed spectral changes is caused by the change in conjugation lengths of PBZT in the dumbbell-shaped ABA triblock copolymers.close6

Synthesis and electrical properties of polyaniline/polyaniline grafted multiwalled carbon nanotube mixture via in situ static interfacial polymerization

The mixture of polyaniline (PANi) and PANi grafted multiwalled carbon nanotube (PANi-g-MWNT) was prepared by a two-step reaction sequence. MWNT was first functionalized with 4-aminobenzoic acid via "direct" Firedel-Crafts acylation in polyphosphoric acid (PPA)/phosphorous pentoxide (P(2)O(5)) medium to afford 4-aminobenzoyl-functionalized MWNT (AFMWNT). Then, aniline was polymerized via an in situ static interfacial polymerization in H(2)O/CH(2)Cl(2) in the presence of AFMWNT in organic phase to yield the mixture of PANi and PANi-g-MWNT. The mixture was characterized with a various analytical techniques such as elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cyclic voltammogram (CV), UV-vis and fluorescence spectroscopies, and electrical conductivity measurement. On the basis of TGA analysis, the thermo-oxidative stability of the mixture was markably improved compared to that of PANi homopolymer. Even after dedoping, in alkaline solution, the mixture would still display semimetallic conductivity (4.9 S/cm). The capacitance of the mixture was also greatly enhanced and its capacitance decay with respect to cycle times was significantly reduced.close131

Defect/Edge-Selective Functionalization of Carbon Materials by Direct Friedel-Crafts Acylation Reaction

Popularly utilized oxidation media, via nitric acid/sulfuric acid mixtures, are too corrosive and oxidizing to preserve structural integrity of highly ordered graphitic materials (carbon nanotubes (CNTs) and graphene). Here, for the most commonly used oxidation method, the important advantages of defect/edge-selective functionalization of carbon materials (CNTs/graphene/graphite) in a polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5) medium are elucidated. The optimized PPA/P2O5 medium is a mild acid that is not only less corrosive than popularly utilized oxidation media, but also has a strong capability to drive Friedel-Crafts acylation by covalently modifying carbon materials. With a broader spectrum of functional groups accessible, the PPA/P2O5-driven Friedel-Crafts acylation offers more options for tailoring the properties and processing of carbon materials