Organic Solvent-soluble Polymers Research Articles

Significant enhancement of bi-directional ultrahigh thermal conductivity in polymer composites fabricated via Polyetherimide@Silver core–shell structured microspheres

Nowadays, the polymer-based composites with excellent thermal-conductive ability and ideal electromagnetic interference shielding performance are in great demand with the advent of developing modern electronic technology. However, most conventional thermal-conductive materials were typically designed to enhance thermal conductivity in just one single direction (through-plane or in-plane direction), which will be inadequate to meet increasing heat-dissipation requirements. Hence, polyetherimide/Silver (PEI/Ag) composites with unique segregated thermal-conductive network were fabricated via hot-pressing the core–shell (PEI@Ag) particles, which was endowed with superior thermal-conductive ability in bi-directions. By this process, the Ag shell was deposited on the surface of various polymer microsphere, and diverse morphology of composite particles would lead to different findings. The results show the PEI@Ag composites with filler content of 18.9 vol% exhibited high in-plane thermal conductivity and through-plane thermal conductivity of 19.9 and 14.0 W/mK, respectively. Particularly, these results achieved obvious improvements of 331 % and 1264 % higher than the composites with filler random distribution, indicating the composite materials obtained outstanding advantage in both horizontal and vertical direction. The research also found that the composites prepared from PEI@Ag core–shell structures possess better properties than those prepared with Ag nanoparticles growing on polymers, indicating the importance of continuous heat-transfer path, and their heat transfer behavior was further demonstrated by finite element analysis. Besides, the composites also exhibited remarkable EMI shielding performance (40.1 dB)). In a word, this study provides viable strategies to enhance the thermal conductivity of composites based on organic solvent-soluble polymer with EMI capability for the development of electronic devices.

N-Benzoyl dithieno[3,2-b:2\u2032,3\u2032-d]pyrrole-based hyperbranched polymers by direct arylation polymerization

BackgroundAlthough poly(N-acyl dithieno[3,2-b:2′,3′-d]pyrrole)s have attracted great attention as a new class of conducting polymers with highly stabilized energy levels, hyperbranched polymers based on this monomer type have not yet been studied. Thus, this work aims at the synthesis of novel hyperbranched polymers containing N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety via the direct arylation polymerization method. Their structures, molecular weights and thermal properties were characterized via 1H NMR and FTIR spectroscopies, GPC, TGA, DSC and XRD measurements, and the optical properties were investigated by UV–vis and fluorescence spectroscopies.ResultsHyperbranched conjugated polymers containing N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety, linked with either triphenylamine or triphenylbenzene as branching unit, were obtained via direct arylation polymerization of the N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole, 2,5-dibromo 3-hexylthiophene and tris(4-bromophenyl)amine (or 1,3,5-tris(4-bromophenyl)benzene) monomers. Organic solvent-soluble polymers with number-average molecular weights of around 18,000 g mol−1 were obtained in 80–92% yields. The DSC and XRD results suggested that the branching structure hindered the stacking of polymer chains, leading to crystalline domains with less ordered packing in comparison with the linear analogous polymers. The results revealed that the hyperbranched polymer with triphenylbenzene as the branching unit exhibited a strong red-shift of the maximum absorption wavelength, attributed to a higher polymer stacking order as a result of the planar structure of triphenylbenzene.ConclusionBoth hyperbranched polymers with triphenylamine/triphenylbenzene as branching moieties exhibited high structural order in thin films, which can be promising for organic solar cell applications. The UV–vis absorption of the hyperbranched polymer containing triphenylbenzene as branching unit was red-shifted as compared with the triphenylamine-containing polymer, as a result of a higher chain packing degree.

Gelatin Nanofiber Matrices Derived from Schiff Base Derivative for Tissue Engineering Applications.

Electrospinning of water-soluble polymers and retaining their mechanical strength and bioactivity remain challenging. Volatile organic solvent soluble polymers and their derivatives are preferred for fabricating electrospun nanofibers. We report the synthesis and characterization of 2-nitrobenzyl-gelatin (N-Gelatin)--a novel gelatin Schiff base derivative--and the resulting electrospun nanofiber matrices. The 2-nitrobenzyl group is a photoactivatable-caged compound and can be cleaved from the gelatin nanofiber matrices following UV exposure. Such hydrophobic modification allowed the fabrication of gelatin and blend nanofibers with poly(caprolactone) (PCL) having significantly improved tensile properties. Neat gelatin and their PCL blend nanofiber matrices showed a modulus of 9.08 ± 1.5 MPa and 27.61 ± 4.3 MPa, respectively while the modified gelatin and their blends showed 15.63 ± 2.8 MPa and 24.47 ± 8.7 MPa, respectively. The characteristic infrared spectroscopy band for gelatin Schiff base derivative at 1560 cm(-1) disappeared following exposure to UV light indicating the regeneration of free NH2 group and gelatin. These nanofiber matrices supported cell attachment and proliferation with a well spread morphology as evidenced through cell proliferation assay and microscopic techniques. Modified gelatin fiber matrices showed a 73% enhanced cell attachment and proliferation rate compared to pure gelatin. This polymer modification methodology may offer a promising way to fabricate electrospun nanofiber matrices using a variety of proteins and peptides without loss of bioactivity and mechanical strength.

Synthesis of hyperbranched conjugated polymers based on 3-hexylthiophene, triphenylamine and benzo [c] [1,2,5] thiadiazole moieties: convenient synthesis through suzuki polymerization and impact of structures on optical properties

Novel 3-hexylthiophene-based hyperbranched conjugated polymers containing triphenylamine and benzo [c] [1, 2, 5] thiadiazole moieties were synthesized by Suzuki coupling polymerization of tris (4-bromophenyl) amine, 2,2′-(3-hexylthiophene-2,5-diyl) bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) and 4,7-dibromobenzo [c] [1, 2, 5] thiadiazole. Organic solvent-soluble polymers with number-average molecular weights of 24,000 and 42,000 g/mol were obtained in 54–57 % yields. Their structures, molecular weights and thermal properties were characterized via proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FT-IR) spectroscopies, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide-angle powder X-ray diffraction (XRD) measurements. Optical investigation by UV–vis and fluorescence spectroscopies revealed that the incorporation of the benzo [c] [1, 2, 5] thiadiazole moiety in the hyperbranched polymer structure resulted in a red-shift of the maximum absorption wavelength and an increase in the solution-photoluminescence quantum yield, indicating an extension of the conjugation length. The UV–vis, DSC and XRD results demonstrated that the aggregation of conjugated polymer chains could effectively be reduced by the hyperbranched structures and that conjugation length extension via the introduction of benzo [c] [1, 2, 5] thiadiazole units led to the coexistence of both crystalline and amorphous phases in the solid state and in solution upon addition of a non-solvent.

Construction of multi-N-heterocycle-containing organic solvent-soluble polymers with 1,3,4,6,9b-pentaazaphenalene

Multi-N-heterocycles could be a useful platform for constructing network structures via hydrogen bonds and for realizing catalyzed organic reactions. In addition, unique optical properties can be achieved by their incorporation into polymers. In this manuscript, the synthesis and characterization of an organic solvent-soluble polymer containing 1,3,4,6,9b-pentaazaphenalene are presented. From a series of optical measurements and comparative studies with model compounds, we investigated the electronic structures of polymer main chains containing the azaphenalene unit. The synthesis and characterization of the organic solvent-soluble polymer containing 1,3,4,6,9b-pentaazaphenalene are presented. From the series of the optical measurements and the comparison studies with the model compounds, we investigated the electronic structures through the polymer main chains involving the azaphenalene unit.

Synthesis, Structure, and Characteristics of Hyperbranched Polyterpene Alcohols

A novel series of bio-based hyperbranched polymers, i.e., hyperbranched polyterpene alcohols, were prepared by the cationic ring-opening polymerizations of citronellol oxide (1) and nopol epoxide (2) using boron trifluoride diethyl etherate (BF3·OEt2) as the catalyst. The polymerizations of 1 and 2 homogeneously proceeded without gelation to produce organic solvent-soluble polymers (poly-1 and poly-2, respectively). The absolute weight-average molecular weights (Mw,MALLS), which were measured by a multiangle laser light scattering instrument (MALLS), were 3700−6200 g mol−1 for poly-1 and 9000−20 000 g mol−1 for poly-2, which were ca. 1.4−4.8 times greater than the relative molecular weights (Mw,SEC) measured by size exclusion chromatography (SEC). The intrinsic viscosities ([η]) of these polymers were very low in the range of 8.5−10.1 mL g−1 for poly-1 and 5.9−9.5 mL g−1 for poly-2. The Mark−Houwink−Sakurada exponent α was calculated to be 0.32−0.40 for poly-1 and 0.25−0.35 for poly-2. These results of the MALLS, SEC, and viscosity measurements suggested that these polymers exist in a compact spherical conformation in solution.

Crowned polyacetylene: 3. Synthesis and cation-binding property of polyphenylacetylene with azacrown cavity by cyclopolymerization of α,ω-bis(4′-ethynylphenoxy)oligooxyethylene containing a pyridyl unit

The cyclopolymerizations of 2,6-bis[7′-(4″-ethynylphenoxy)-2′,5′-dioxaheptyl]pyridine ( 1a) and 2,6-bis[10′-(4″-ethynylphenoxy)-2′,5′,8′-trioxadecyl]pyridine ( 1b) were carried out using the (bicyclo[2.2.1]hepta-2,5-diene)rhodium(I) chloride dimer. The yellowish powdery, organic solvent-soluble polymers were obtained using an amine as a cocatalyst. The resulting polymers consisted of cyclic constitutional repeating units as the main structure along with pendant acetylenic groups, i.e. the extent of cyclization was from 0.89 to 0.99 for the polyphenylacetylenes with an azacrown cavity, 2a and 2b, obtained from monomers 1a and 1b, respectively. Polymer 2 exhibited cation-binding ability for alkaline earth metal, heavy metal, and transition metal ions and, in particular, for Ag +. The complex of 2 with Ag +, which was confirmed by the 1H n.m.r. spectrum, consisted of the azacrown cavity and Ag + with a ratio of 2.