Rodlike Poly Research Articles

Flow-accelerated polycondensation reaction to prepare rigid rodlike poly(p-phenylene-cis-benzobisoxazole)

Under the conditions specified in this work, the polycondensation reaction to prepare rigid rodlike poly(p-phenylene-cis-benzobisoxazole) (PBO) is diffusion-controlled. This work aims to study the flow-driven polycondensation reaction of PBO. The effect of mixing efficiency through changing the stirring speed on the polycondensation reaction of PBO was first investigated in a paddle impeller reactor (PIR). In the initial stage of polymerization, the increase of stirring speed is obviously conducive to accelerating the polycondensation reaction. However, the promoting effect of stirring speed on the polycondensation reaction is greatly reduced in the middle and late stages of polymerization. The effect of the flow pattern with different proportions of shear flow, elongational flow and rotational flow on the polycondensation reaction of PBO was further investigated by comparing three reactors including Couette-Taylor reactor (CTR) with a complete shear flow, PIR with strong shear and elongational flows, and double helical ribbon reactor (DHR) with strong shear and rotational flows. Result shows that the improvement of proportions of rotational flow and elongational flow is beneficial to accelerate the polycondensation reaction of PBO in the middle and late stages of polymerization, especially for the rotational flow.

Stiffness-Dependent Intracellular Location of Cylindrical Polymer Brushes.

Cylindrical polymer brushes (CPBs) are macromolecules with nanoparticle proportions. Their modular synthesis enables tailoring of their chemical composition as well as the dialing-up of overall dimensions and physicochemical properties. In this study, two rod-like poly[(ethylene glycol) methyl ether methacrylate] (PEGMA)-based CPBs with varying stiffness but otherwise comparable features and functionality, are synthesized. Differences in particle stiffness are assessed using small angle neutron scattering (SANS). It is observed that the fate of the two CPBs within cells is distinctly different. Stiffer CPBs seem to gravitate toward the mitochondria, whereas CPBs with reduced stiffness are present in different intracellular vesicles.

Effect of humidity and temperature on proton conduction in phosphonated copolymers

Phosphonated block copolymers based on poly(vinylbenzyl phosphonic acid) are examined under varied humidity and temperatures for their proton conducting properties. The copolymers have rod-like poly(phenylene oxide) block that induces ordered domains. The ordered and crystalline domains are associated with higher proton conductivity. The highest conductivity approaching 10−2 S/cm was determined under ambient conditions for the copolymer with a rather shorter PPO block. Scanning electron microscopy images of the copolymer reveal interconnected ionic domains that are related directly with the higher conduction in phosphonated block copolymer. A comparative study with sulfonated Nafion suggests that phosphonated polymers too can be used in fuel cell operating at a high temperature range.

Controlled Phase Separation in Poly( p-phenyleneethynylene) Thin Films and Its Relationship to Vapor-Sensing Properties.

In this paper, we report the synthesis and mesoporous film formation of hydrophobic rodlike poly( p-phenyleneethynylene)s (PPEs) and present porosity-dependent quenching studies using 1,3,5-trinitrotoluene (TNT) vapors. Nonsolvent vapor-induced phase separation was used to induce pore formation during film casting, and the concentration of PPEs in the casting solution was controlled carefully to prevent excimer formation. We found that the structures of the sidechains of the PPEs strongly influence the range of relative humidity at which controlled pore generation occurs, which could be rationalized from interfacial energies calculated from contact angle measurements. Porosity of the PPE films resulted in increased efficiency of fluorescence quenching toward TNT vapors, which previously required very thin films (below 5 nm) for sensing applications. The control of the porous structure as well as film thickness constitutes a promising strategy for enhancing the efficiency of chemosensors and in more general applications requiring fine-tuned polymer-gas interactions.

Rod-like transition first or chain aggregation first? ordered aggregation of rod-like poly(p-phenyleneethynylene) chains in solution.

The rod-like configuration of conjugated polymer chains with its low energetic disorder is the key to utilizing the backbone as a highly electrically-conductive wire. An energetic disorder that is higher than 0.1 eV, coupled with vibronic modes of the chains, leads to the localization of charges. Herein, we have tracked precisely the rod-like transition of poly(p-phenyleneethynylene) (PPE) chains as a function of temperature in diluted solutions, and shown a steep increase in persistence length at 230 K. The resulting rod-like configuration of the PPE chains with its extended electronic conjugation exhibited an extremely small energetic disorder of ∼70 meV, and was stabilized by subsequent polymer aggregate formation.

Preparation of poly(ionic liquid) nanoparticles through RAFT/MADIX polymerization-induced self-assembly

The first RAFT/MADIX polymerization-induced self-assembly (PISA) system was successfully developed for the preparation of rod-like poly(ionic liquid) (PIL) nanoparticles.

Toward Truly Water-Soluble Rodlike Polyelectrolytes: Protonation-Deprotonation Equilibria in Aqueous Solutions of Poly(para-phenylenes) Wrapped in Ethylene oxide and Amino Side Groups

The protonation/deprotonation behavior of rodlike poly(p-phenylene)-based polyamines is analyzed in aqueous solution using NMR spectroscopy and potentiometry. The observed features cannot be explained by a single acid constant, but shifting electrostatic potential—generated by the protonated ammonium side groups—has to be taken into account additionally. Consequently, the density of ionic groups attached to the polymer backbones and the ionic strength of the solutions contribute to the polybase behavior as well: the shift of basicity as observed with increasing degrees of protonation can be quantified by an apparent ionization constant, pKapp, for each value of pH. Due to intrinsic rigidity of the polymer backbone and true solubility in water effectuated by the highly polar side chains, the electrostatic effects influencing the polybase behavior can be observed free from conformational effects and over the whole range of accessible pH and degree of protonation for the first time.

Tunable Triple‐Shape Memory Binary Mixtures with High Transition Temperature and Robust Mechanical Properties

High temperature triggered shape memory polymers are currently attracting considerable attention due to their potential applications in the context of harsh environments. Herein, tunable dual‐ and triple‐shape memory binary mixture polyimides with high transition temperatures that may meet some of these requirements are presented. The binary mixtures are prepared by blending two poly (amic acid)s of rodlike poly(benzoxazole‐imide) (PIB) and flexible polyetherimide (PIO), followed by solvent evaporation and thermal imidization. The aggregation structures, thermal mechanical properties, and shape memory behaviors are systematically studied. It is found that dual‐shape memory cycles give excellent shape fixity and recovery of up to 98 and 97%. Moreover, binary mixtures with broad glass transition temperatures endow good triple‐shape memory effects and the shape memory at each step crucially depends on the content of the PIB due to the enhancement of physical crosslinks. Additionally, their thermally tough and mechanically strong properties would suggest wide potential applications of the mixtures. image

Solvent Tunable Self-Assembly of Amphiphilic Rod–Coil Block Copolymers with Chiral, Helical Polycarbodiimide Segments: Polymeric Nanostructures with Variable Shapes and Sizes

The nanoscale self-assembly of four amphiphilic rod–coil di- and triblock copolymers with chiral, rodlike poly(N-1-phenethyl-N′-methylcarbodiimide) (PPMC) segments and random coil, hydrophilic PEG blocks has been investigated using dynamic light scattering (DLS) and tapping-mode atomic force microscopy (AFM). This self-assembly proved to be highly tunable simply upon altering the concentration and chemical structure of the hydrophilic selective solvent and/or blending the copolymers with polycarbodiimide homopolymer. When spin-coated from dilute (c = 0.5 mg/mL) THF/H2O solutions, these interesting polymers adopted either simple spherical micelles or spherical polymersomes depending on the relative amount of H2O used for dissolution. Switching selective solvent from H2O to MeOH induced changes in aggregation behavior, as evidenced by DLS and AFM, with interesting nanoworm and nanomaggot micelle assemblies observed when spin-coated from dilute THF/MeOH solutions. Blending high-MW PPMC homopolymer with the b...

Anions behaviors for the dimensionalities of coordination polymers based on poly(imidazole) ligands

Abstract To explore the influence for the dimensionalities of coordination polymers, in presence of different anions with different behaviors, three new coordination polymers with different dimensionalities have been prepared by reacting M2+ (M = Zn or Co) with two structurally related rod-like poly(imidazole) ligands, 1,4-bis(benzoimidazol-1-yl)-phenyl (L1) and 1,4-bis(imidazol-1-yl)-phenyl (L2). Such three new coordination polymers with different architectures, [Zn(L1)(NO3)2]n (1), {[Zn(L2)2]·2BF4·2HCCl3·2H2O}n (2) and [Co(L2)(SO4)]n (3), have been determined by single-crystal X-ray diffraction analysis and characterized by elemental analysis, and IR analysis. Complex 1 is alternative linked by octahedral Zn centers and the ligand L1 to exhibit a one-dimensional (1D) chain structure. However, complexes 2 and 3 both present layered structures contain a similar -L(ligand)–M(metal)-L–M- chain motifs that found in complex 1. In complex 2, each Zn(II) ion is coordinated by four different L2 to form a undulated sheet. Complex 3 also present a undulated sheet structure, however, they were connected by the SO 4 2 - group and the L2 ligands, different from only of the L2 ligands in complex 2. The result indicates that the different anions behaviors could be the great influence on the degree of dimensionality of coordination polymers.

Self-assembly of cationic rod-like poly(2,5-pyridine) by acidic bis(trifluoromethane)sulfonimide in the hydrated state: A highly-ordered self-assembled protonic conductor

We show that acid–base complexation of rod-like poly(2,5-pyridine) (PPY) by bis(trifluoromethane)sulfonimide (TFSI) leads to highly-ordered lamellar self-assemblies in the hydrated films and shows relatively high room temperature conductivity of ca. 10−4 S/cm. Thin films with different nominal degrees of complexation were studied using X-ray diffraction, Fourier transform infrared spectroscopy, contact angle measurements, conductivity measurements, and polarised optical microscopy. We propose that the self-assembly is promoted by the amphiphilicity of TFSI and the interplay between the hydrophilic and hydrophobic sites within the complexes. The hydrophilic sites allow confinement of water molecules within the hydrated self-assemblies for low loading of TFSI to promote proton conductivity. For high loading of TFSI in the hydrated state, another coincident self-assembled structure is additionally observed, which we suggest to form due to phase separated water/TFSI domains, as resembling lamellar water/surfactant liquid crystalline phases. The new type of self-assembled acid–base material combining rod-like polymeric cations and ionic liquid anions suggests new routes for ionic and protonic transport and functional materials.

ChemInform Abstract: High-Spin Polyphenoxyl Based on Poly(1,4-phenyleneethynylene).

Rodlike poly(1,4-phenyleneethynylene) 2-substituted with multiple pendant phenoxyls 1 was synthesized by polymerizing 4-bromo-2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethynylbenzene 10a using the catalyst of a palladium−triphenylphosphine complex and cuprous iodide and subsequent heterogeneous oxidation. The corresponding dimer 2 was also synthesized; X-ray analysis of its precursor 4 indicated a linear phenyleneethynylene backbone and twisted dihedral angles of 50 and 77° for the pendant phenol groups. ESR spectra suggested a delocalized spin distribution from the pendant phenoxyl to the backbone. The diphenoxyl 2 had a triplet (S = 2/2) ground state. The spin concentration of the polyphenoxyl 1 could not be increased beyond 0.7 spin/unit due to its low solvent solubility; 1 with a spin concentration of 0.62 had an average S of 3/2.

Effect of Length on the Diffusion of a Rodlike Polymer at Concentrations Spanning the Isotropic−Lyotropic Transition

The optical tracer self-diffusion of rodlike poly(benzyl-alpha,l-glutamate) (PBLG) is measured in pyridine solutions spanning the isotropic-liquid crystalline phase boundary for two different molecular weights, M = 134 500 (contour length L = 921 A, axial ratio x = 58) and M = 24 600 (L = 168 A, x = 10.5). The results are compared to previously published data for PBLG with M = 232 000 (L = 1590 A, x = 99). Under the conditions of the measurements, the two longer rodlike polymers align in the liquid crystalline phase with their cholesteric screw axis in the vertical direction. The diffusion is measured in a particular direction normal to this over distances that are long compared to the polymer lengths. Except for the shortest polymer, whose cholesteric screw axis does not assume the vertical alignment, the diffusion suddenly increases as the liquid crystalline phase is entered, then declines, signaling the disappearance of topological constraints in the isotropic phase having a vertical component. The solutions also contain a small, fluorescent component whose mobility was not at all affected by the isotropic-liquid crystalline phase transition.

Optical absorption and emission of fully conjugated heterocyclic aromatic rigid-rod polyelectrolytes containing sulfonated pendants

Fully conjugated and rodlike poly[(1,7-dihydrobenzo[1,2-ḏ:4,5-d′]diimidazole-2,6-diyl)-2-(2-sulfo)-p-phenylene] (sPBI) was synthesized and fabricated for monolayer light emitting diodes showing a threshold voltage of 4.5 V and an emission λmax of 530 nm. Intractable sPBI was derivatized for a fully conjugated water soluble rigid-rod polyelectrolyte sPBI-PS(Li+) which was doped with LiCF3SO3 or LiN(CF3SO2)2 for optical absorption, electrical conductivity, and luminescent emission. sPBI-PS(Li+) light emitting electrochemical cells doped with 0.41 and 1.01 wt % of LiN(CF3SO2)2 showed a threshold voltage of 2.8 V and a tenfold increase in electroluminescence intensity (at λmax=514 nm) which did not increase with its conductivity.

Successive Synthesis of Well-Defined Star-Branched Polymers by Iterative Methodology Based on Living Anionic Polymerization

The subject of this review is to introduce a novel iterative methodology based on living anionic polymerization using specially designed 1,1-diphenylethylene (DPE) derivatives recently developed for the synthesis of well-defined many armed star-branched polymers with same or chemically different arm segments. The methodology basically involves only two sets of the following reaction conditions for the entire iterative synthetic sequence: (a) a linking reaction of a living anionic polymer with a DPE-chain-functionalized polymer, and (b) an in situ reaction of a DPE-functionalized agent with the anion generated by the linking reaction to reintroduce the DPE functionality usable for the next reaction. The number of arms to be linked by each stage of the iteration depends on the starting core and DPE-functionalized agents and can dramatically increase by the agent of choice. New functional asymmetric star-branched polymers involving conductive and rigid rod-like poly(acetylene) segment(s) have been synthesized by the methodology using the intermediate polymer anions produced by the linking reaction as macroinitiators to polymerize 4-methylphenyl vinyl sulfoxide, followed by thermal treatment of the resulting star-branched polymers.

Single short-chain conjugated polymer studied with optical spectroscopy: A donor-accepter system

Single rodlike poly[2-methoxy, 5-(${2}^{\ensuremath{'}}$-ethyl-hexyloxy)-$p$-phenylene-vinylene] (MEH-PPV), in which the chain length supports only two or three chromophores, was studied using optical spectroscopy in order to elucidate exciton dynamics within a single conjugated polymer. Emission at one to three discrete intensity levels coupled with on/off blinking was seen in the fluorescence time traces. Drops in emission intensity were accompanied in the majority of cases by an abrupt spectral blueshift and a corresponding increase in the fluorescence lifetime. Photon correlation measurements indicated that at any point in time there was only one emitter active. This suggests that the two or three chromophores in a short-chain polymer act as a typical donor-acceptor system with energy absorbed by the donors (shorter chromophores) transferring to the acceptor (longer chromophore) along the polymer backbone before emission. Once the acceptor is quenched, a donor takes turns to emit.

Characterization of Rodlike Poly(n-hexyl isocyanate) Macromonomers and Their Polymacromonomers by Light Scattering, SAXS, Intrinsic Viscosity, and Scanning Force Microscopy

SEC-MALS, small-angle X-ray scattering (SAXS), and viscosity measurements were made on tetrahydrofuran (THF) and n-hexane of a series of 4-vinylbenzyl and methacrylate ended poly(n-hexyl isocyanate) (PHIC) macromonomers (VB-HIC-n and MA-HIC-n, where n is a degree of polymerization of HIC and in a range from 21 to 192), together with higher molecular weight PHIC chains than the macromonomers. The molecular weight dependence of z-average mean-square radius of gyration z and intrinsic viscosity [η] of the macromonomers and PHIC chains in THF at 25 °C were quantitatively described by the wormlike chain model with the stiffness parameter (λ−1)=63nm, the molecular weight per unit contour length (ML)=725 nm−1, and the hydrodynamic diameter (dB)=1.6 nm. The SAXS scattering profile of VB-HIC-57 in n-hexane at 25 °C was also perfectly described in terms of the straight cylinder model. The results imply that the macromonomers may be regarded as a rigid rod molecule in THF and n-hexane. Cylindrical brushes consisting of polystyrene as a main chain and PHIC chains as a side chain were prepared by homopolymerizations of VB-HIC-46 and their dimensional properties were investigated in THF at 25 °C by SAXS and SEC-MALS measurements. The molecular weight dependence of z of the brushes was quantitatively explained by the wormlike cylinder model with the parameters of λ−1=48 nm, ML=2.40×104 nm−1, the cross-sectional radius of gyration of the cylinder o1/2=4.66 nm, and the end effect (δ=16.7 nm) arising from side chains near the main-chain ends. It was concluded, therefore, that the main chain stiffness of the brush remarkably increases by the presence of densely located rodlike side chains. Direct observation of single brush of the poly(VB-HIC-46) deposited on a mica was made by scanning force microscopy (SFM) to reveal the cylindrical brushes consisting of rodlike side chains with ca. 15 nm in a thickness.

Molecular Reorganization of Rod−Coil Diblock Copolymers at the Air−Water Interface

Amphiphilic rod-coil diblock copolymers consisting of flexible poly(ethylene oxide) (PEO) and rodlike poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS) with predominant hydrophobic contents formed ordered monolayers at the air-water interface. The structures of monolayers transferred to a mica substrate at different surface pressures by the Langmuir-Blodgett method were investigated by atom force microscopy (AFM). For PEO(104)-b-PMBPS(17) copolymer (the subscripts denote the number-averaged polymerization degree of each block), a complete spectrum of molecular reorganization at variable surface pressures was observed. Spherical surface aggregates of LB monolayers were spontaneously formed during the solvent evaporation after the deposition of polymer solution. Continuous compression led to the pancake-to-brush conformation transition of the copolymer that PEO chains desorbed from the air-water interface and went into the water subphase. The effective content of the rod block changed continuously from 61% at zero pressure to 93% at the start of the monolayer collapse, igniting the molecular reorganization. As a result, coalescence of individual spherical aggregates into long cylindrical aggregates with an increase of the surface pressure was observed. For a series of block copolymers PEO(104)-b-PMBPS(m)() (m = 17, 30, 45, 53), as the rod contents increased from 61% to 83%, the morphological transition from spherical aggregates to long cylindrical aggregates in orientational order developed at zero pressure, which showed a similar dependence on the effective contents of the rod block to PEO(104)-b-PMBPS(17) at different pressures. In comparison to coil-coil block copolymers PEO-b-PS, the rod-coil block copolymers PEO-b-PMBPS exhibited distinct structure reorganization behavior, in which the orientation of rod block might play an important role.

Preparation of styryl-ended rod-like poly(n-hexyl isocyanate) macromonomers and their radical co-polymerization behavior with styrene

Styryl-ended rod-like macromonomers consisting of poly(n-hexyl isocyanate) (2) (VB-HIC-n, where n is a degree of polymerization varying from 9 to 75) with relatively narrow molecular weight distribution (M w/M n < 1.2) have successfully been prepared in CH2Cl2 at room temperature by living coordination polymerization of n-hexyl isocyanate (HIC) using 4-vinylbenzyloxy-dichloro(cyclopentadienyl)titanium(IV) (1) as an initiator. The radical co-polymerization behavior of the rod-like macromonomers with styrene has been studied and summarized as a function of degree of polymerization of HIC. The apparent co-polymerizabilities of the rod-like macromonomer seem to be almost equivalent to styrene, suggesting that the reactivity is mainly determined by the chemical reactivity of the ended double bond.

Functional polymeric materials: complexing amphiphiles as structure‐inducing elements

AbstractSelf‐assembly of polymeric comb‐shaped supramolecules is a powerful tool to prepare functional materials. Enhanced conductivity due to hexagonal self‐organization of conducting polyaniline and polarized photoluminance in solid‐state films of rodlike poly(2,5‐pyridinediyl) obtained by removing hydrogen‐bonded side chains from the aligned thermotropic smectic phase are two examples. Hierarchically structured materials are formed when the self‐organization of block copolymers is combined with that of comb‐shaped supramolecules. These form the basis for tunable nanoporous membranes, nano‐objects and materials with anisotropic properties such as tridirectional proton conductivity.