Poly(oxyethylene methacrylate)–poly(4-vinyl pyridine) comb-like polymer electrolytes for solid-state dye-sensitized solar cells

Poly(oxyethylene methacrylate)–poly(4-vinyl pyridine) (POEM–P4VP) comb-like copolymers with 3:7, 5:5, and 6:4 wt ratio were synthesized via atom transfer radical polymerization and confirmed by ¹H-NMR and FT-IR spectroscopy. The copolymers were quaternized with 1-iodopropane to convert the pyridine groups into pyridinium ions, i.e., POEM–qP4VP. Transmission electron microscopy showed that strongly segregated microphase separation in POEM–P4VP was less prominent upon quaternization due to interactions between the ether oxygens of POEM and the quaternized pyridine groups of qP4VP, as confirmed by FT-IR spectroscopy. The energy conversion efficiencies of dye-sensitized solar cells (DSSCs) with quaternized polymer electrolytes were always greater than those with pristine electrolytes due to greater ionic conductivity and concentrations of free iodide ions. The maximum energy conversion efficiency of a DSSC employing POEM–qP4VP electrolyte reached 3.0% at 100 mW/cm² when a 6:4 wt.% of POEM–qP4VP was used.     

A well-defined diblock copolymer of poly-(ethylene oxide)-block-poly (4-vinylpyridine) for separation of basic proteins by capillary zone electrophoresis

A series of well-defined diblock copolymers, poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-P4VP) used as physical coating of capillaries, were synthesized by atom transfer radical polymerization (ATRP). EOF measurement results showed that all synthesized PEO-b-P4VP diblock copolymer-coated capillaries in this report could suppress EOF effectively compared to the bare fused-silica capillaries, and efficient separations of basic proteins were achieved. The effects of the molecular weight of P4VP block in PEO-b-P4VP and buffer pH on the separation of basic proteins for CE were investigated in detail. Moreover, the relationships between morphologies of PEO-b-P4VP diblock copolymers in buffer, which were studied by transmission electron microscopy, and the separation efficiencies of basic protein with PEO-b-P4VP diblock copolymers coatings were discussed.     

四臂星型聚苯乙烯-聚4-乙烯基吡啶嵌段共聚物纤维状胶束及负载金纳米粒子的研究

通过两步原子转移自由基聚合,制备了4种不同嵌段长度的四臂星型嵌段共聚物苯乙烯-聚4-乙烯基吡啶嵌段共聚物(PS-b-P4VP)4.在选择性溶剂甲苯中,随着嵌段长度的变化,自组装胶束的形态从球型到短棒状和纤维状的转变,其中(PS25-b-P4VP90)4自组装形成的以P4VP为核,以PS为花瓣型壳的纤维状胶束.以这种纤维状胶束作为模板,制备了金纳米粒子均匀分布的一维纳米材料     

多嵌段共聚物(P4VP-b-PS-b-P4VP)_n的胶束化行为研究

研究了一系列具有不同链段长度和组成的聚4-乙烯基吡啶-聚苯乙烯-聚4-乙烯基吡啶多嵌段共聚物(P4VP-b-PS-b-P4VP)n在其选择性溶剂甲苯和pH<3的水中的胶束化过程,主要研究了多嵌段共聚物链段长度、溶液浓度和溶剂对其胶束形态的影响.透射电镜和原子力显微镜结果表明随着P4VP段链的相对增长,多嵌段共聚物在甲苯中的胶束形态由蠕虫链状向短棒状到球状胶束变化,而其在pH<3的水溶液中均形成球形胶束.由于特殊的链结构,聚合物的浓度对(P4VP-b-PS-b-P4VP)n多嵌段共聚物的胶束行为和胶束形态有着重要的影响.同时,(P4VP-b-PS-b-P4VP)n多嵌段共聚物分子量分布的多分散性对其在选择性溶剂中的胶束形态也有所影响.     

Smart assembly behaviors of hydroxypropylcellulose-graft-poly(4-vinyl pyridine) copolymers in aqueous solution by thermo and pH stimuli

Thermo- and pH-sensitive graft copolymers, hydroxypropylcellulose-graft-poly(4-vinyl pyridine) (HPC-g-P4VP), were synthesized via atom transfer radical polymerization (ATRP) and characterized. The thermo- and pH-induced micellization and stimuli-responsive properties of HPC-g-P4VP graft copolymers in aqueous solution were investigated by transmittance, (1)H NMR, dynamic light scattering (DLS), and so on. For the pH-induced micellization, the P4VP side chains collapse to form the core of the micelles, and the HPC backbones stay in the shell to stabilize the micelles. In the case of thermoinduced micellization, the HPC backbones collapse to form the core of the micelles that was stabilized by the P4VP side chains in the shell upon heating. What's more, the cloud point of the HPC-g-P4VP copolymers in the aqueous solution could be finely tuned by changing the length of P4VP side chains or the pH values. In acidic water, the longer the side chains, the higher the cloud point. For those HPC-g-P4VP copolymers with short side chains, for example, HPC0.05-g-P4VP(3), the lower pH correlates a higher cloud point. The thermo- or pH-induced micelles also have the pH- or thermosensitivity due to their P4VP or HPC shells.     

Grafting of 4-Vinyl Pyridine onto Nylon-6 Initiated by Redox System

The graft copolymerization of 4‐vinyl pyridine (4VP) onto nylon‐6 (PA6) was studied by using potassium diperiodatonickelate(IV) (DPN)‐PA6 redox system in alkaline medium. The structures of graft copolymers were confirmed by Fourier transfer infrared spectroscopy (FTIR) and X‐ray diffraction. The properties of graft copolymers were investigated by thermogravimetric analysis (TGA). A mechanism was proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, the ratio of 4VP to PA6, pH as well as reaction temperature and time were investigated. Graft copolymers with high grafting efficiency (>95%) were obtained, which indicated that DPN‐PA6 redox system is an efficient initiator for this graft copolymerization. The quaternized PA6‐g‐P4VP (QPAVP) was proved to be an excellent adsorbent to heavy metal ions.     

Charges of soluble amphiphiles and particles: random and diblock copolymerizations of MAA/AAm,MAA/St,and MAA/4VP in ethanol

Random and reversible addition-fragmentation chain transfer (RAFT) copolymerizations of methacrylic acid (MAA)/acrylamide (AAm), MAA/styrene (St), and MAA/4-vinyl pyridine (4VP) were carried out in ethanol. (CPDB)-terminated PMAA (PMAA-CPDB) and 2,2′-azobis(2,4-diemthylvaleronitrile) (V-65) was used as the macromolecular chain transfer agent (CTA) and initiator, respectively. Electric conductivity of copolymerization systems was traced throughout the polymerizations, and charges of soluble copolymer and particles were detected. As a result, a considerable increase of conductivity was observed in all of the RAFT polymerization systems, whereas the variation of conductivity in the random copolymerization systems was insignificant. The high conductivity of RAFT polymerization was dominantly contributed by the soluble diblock copolymers in the serum, rather than their particles, except for P(MAA-b-4VP) where only the particles was obtained due to the zwitterionic interactions of PMAA segments and 4VP. In the direct current (DC) field, the behavior of these soluble diblock copolymers, P(MAA-b-AAM) and P(MAA-b-St), indicated that they were positively charged, whereas the particles of (PMAA-b-AAm) and P(MAA-b-4VP) were surprisingly negatively charged, though the composition of MAA was dominant. Soluble random copolymers of P(MAA-co-St) and P(MAA-co-4VP) represented the charge neutrality. These results indicated that the positive charges were contributed by the solvophobic block in the soluble diblock copolymers. Therefore, the diblock copolymers were the macrodipoles boosting the conductivity of solution. Meanwhile, it indicated that the electrostatic interactions of dipoles were possibly the main driving force of their self-assembly. Generally, compared with RAFT polymerization, the particles were hard to be prepared in the random copolymerization. It implies that the electrostatic interactions of diblock copolymers also played an important role in the particle formation.

Miscibility of polysulfone blends with poly(1‐vinylpyrrolidone‐co‐styrene) copolymers and their interaction energies

The miscibility of polysulfone (PSf) with various hydrophilic copolymers was explored. Among these blends, PSf gave homogeneous mixtures with poly(1‐vinylpyrrolidone‐co‐styrene) [P(VP–S)] copolymers when these copolymers contained 68–88 wt % 1‐vinylpyrrolidone (VP). Miscible PSf blends with P(VP–S) copolymers underwent phase separation on heating caused by lower critical solution temperature (LCST)‐type phase behavior. The phase behavior depended on the copolymer composition. Changes in the VP content of P(VP–S) copolymers from 65 to 68 wt % shifted the phase behavior from immiscibility to miscibility and the LCST behavior. The phase‐separation temperatures of the miscible blends first increased gradually with the VP content, then went through a broad maximum centered at about 80 wt % VP, and finally decreased just before the limiting content of VP for miscibility with PSf. The interaction energies of binary pairs involved in PSf/P(VP–S) blends were evaluated from the phase‐separation temperatures of PSf/P(VP–S) blends with lattice‐fluid theory combined with a binary interaction model. The decrease in the contact angle between water and the membrane surface with increasing VP content in P(VP–S) copolymers indicated that the hydrophobic properties of PSf could be improved via blending with hydrophilic P(VP–S) copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1401–1411, 2003     

Synthesis of arborescent polystyrene‐g‐[poly(2‐vinylpyridine)‐b‐polystyrene] core–shell–corona copolymers

Arborescent copolymers with a core‐shell‐corona (CSC) architecture, incorporating a polystyrene (PS) core, an inner shell of poly(2‐vinylpyridine), P2VP, and a corona of PS chains, were obtained by anionic polymerization and grafting. Living PS‐b‐P2VP‐Li block copolymers serving as side chains were obtained by capping polystyryllithium with 1,1‐diphenylethylene before adding 2‐vinylpyridine. A linear or arborescent (generation G0 – G3) PS substrate, randomly functionalized with acetyl or chloromethyl coupling sites, was then added to the PS‐b‐P2VP‐Li solution for the grafting reaction. The grafting yield and the coupling efficiency observed in the synthesis of the arborescent PS‐g‐(P2VP‐b‐PS) copolymers were much lower than for analogous coupling reactions previously used to synthesize arborescent PS homopolymers and PS‐g‐P2VP copolymers from the same types of coupling sites. It was determined from static and dynamic light scattering analysis that PS‐b‐P2VP formed aggregates in THF, the solvent used for the synthesis. This presumably hindered coupling of the macroanions with the substrate, and explains the low grafting yield and coupling efficiency observed in these reactions. Purification of the crude products was also problematic due to the amphipolar character of the CSC copolymers and the block copolymer contaminant. A new fractionation method by cloud‐point centrifugation was developed to purify copolymers of generations G1 and above. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1075–1085     

Synthesis of poly(N-isopropylacrylamide)-b-poly(2-vinylpyridine) block copolymers via RAFT polymerization and micellization behavior in aqueous solution

Poly(N-isopropylacrylamide)-b-poly(2-vinylpyridine) (PNIPAM-b-P2VP) block copolymers were synthesized for the first time via reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of S-1-dodecyl-S(')-(a,a(')-dimethyl-a(')-acetic acid)trithiocarbonate as chain transfer agent (CTA) and 2,2(')-azobis(isobutyronitrile) as initiator. Both pH- and thermo-induced micellization behavior of the PNIPAM(59)-b-P2VP(102) block copolymer in dilute aqueous solution was investigated by pyrene fluorescence, dynamic and static light scattering, transmission electron microscopy and (1)H NMR. The results show that the critical aggregation pH value of the block copolymer is around 5 and the critical aggregation temperature of the block copolymer is around 42 degrees C. A reversible transition between P2VP-core and PNIPAM-core micelles can be observed through an intermediate unimer state in aqueous solution.     

P (VDF‐co‐CTFE)‐g‐P2VP amphiphilic graft copolymers: Synthesis,structure, and permeation properties

A series of amphiphilic graft copolymers of poly (vinylidene fluoride‐co‐chlorotrifluoroethylene)‐g‐poly(2‐vinyl pyridine), P (VDF‐co‐CTFE)‐g‐P2VP, with different degrees of P2VP grafting (from 26.3 to 45.6 wt%) was synthesized via one‐pot atom transfer radical polymerization (ATRP). The amphiphilic properties of P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers allowed itself to self‐assemble into nanoscale structures. P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers were introduced into neat P (VDF‐co‐CTFE) as additives to form blending membranes. When two different solvents, N‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF), were used, specific organized crystalline structures were observed only in the NMP systems. P (VDF‐co‐CTFE)‐g‐P2VP played a pivotal role in controlling the morphology and pore structure of membranes. The water flux of the membranes increased from 57.2 to 310.1 L m^?2 h^?1 bar^?1 with an increase in the PVDF‐co‐CTFE‐g‐P2VP loading (from 0 to 30 wt%) due to increased porosity and hydrophilicity. The flux recovery ratio (FRR) increased from 67.03% to 87.18%, and the irreversible fouling (R_ir) decreased from 32.97% to 12.82%. Moreover, the pure gas permeance of the membranes with respect to N₂ was as high as 6.2 × 10⁴ GPU (1 GPU = 10^–6 cm³[STP]/[s cm² cmHg]), indicating their possible use as a porous polymer support for gas separation applications.     

Creating surfactant nanoparticles for block copolymer composites through surface chemistry

A simple strategy to tailor the surface of nanoparticles for their specific adsorption to and localization at block copolymer interfaces was explored. Gold nanoparticles coated by a mixture of low molecular weight thiol end-functional polystyrene (PS-SH) (Mn = 1.5 and 3.4 kg/mol) and poly(2-vinylpyridine) homopolymers (P2VP-SH) (Mn = 1.5 and 3.0 kg/mol) were incorporated into a lamellar poly(styrene-b-2-vinylpyridine) diblock copolymer (PS-b-P2VP) (Mn = 196 kg/mol). A library of nanoparticles with varying PS and P2VP surface compositions (FPS) and high polymer ligand areal chain densities was synthesized. The location of the nanoparticles in the PS-b-P2VP block copolymer was determined by transmission electron microscopy. Sharp transitions in particle location from the PS domain to the PS/P2VP interface, and subsequently to the P2VP domain, were observed at FPS = 0.9 and 0.1, respectively. This extremely wide window of FPS values where the polymer-coated gold nanoparticles adsorb to the interface suggests a redistribution of PS and P2VP polymers on the Au surface, inducing the formation of amphiphilic nanoparticles at the PS/P2VP interface. In a second and synthetically more challenging approach, gold nanoparticles were covered with a thiol terminated random copolymer of styrene and 2-vinylpyridine synthesized by RAFT polymerization. Two different random copolymers were considered, where the molecular weight was fixed at 3.5 kg/mol and the relative incorporation of styrene and 2-vinylpyridine repeat units varied (FPS = 0.52 and 0.40). The areal chain density of these random copolymers on Au is unfortunately not high enough to preclude any contact between the P2VP block of the block copolymer and the Au surface. Interestingly, gold nanoparticles coated by the random copolymer with FPS = 0.4 were dispersed in the P2VP domain, while those with FPS = 0.52 were located at the interface. A simple calculation for the adsorption energy to the interface of the nanoparticles with different surface arrangements of PS and P2VP ligands supports evidence for the rearrangement of thiol terminated homopolymers. An upper limit estimate of the adsorption energy of nanoparticles uniformly coated with a random arrangement of PS and P2VP ligands where a 10% surface area was occupied by P2VP -mers or chains was approximately 1 kBT, which indicates that such nanoparticles are unlikely to be segregated along the interface, in contrast to the experimental results for nanoparticles with mixed ligand-coated surfaces.     

Synthesis and optical properties of white phosphorescent carbazole - iridium copolymers

A series of novel carbazole-iridium copolymers have been designed and synthesized by the combination of blue-emitting acrylate carbazole M1 with hole transporting property and yellow-emitting cyclometalated iridium complex M2 containing 2-phenylpyridine as main ligand and acrylic acid as auxiliary ligand. The results showed that the blue carbazole host resulted in an efficient energy transfer to the yellow iridium complex guest, and when the feed molar ratio of M1 to M2 was 99:1, the emission spectrum of the copolymer presented a broad peak emission which can cover the whole visible range from 400 to 700 nm to obtain a nearly white copolymer material with the CIE coordinates of (0.30, 0.31), as a consequence of polymerized units luminescence, host-guest energy transfer and conjugation degree. Nevertheless, the host-guest energy transfer resulted in green emission about 524 nm of copolymer as the proportion of iridium complex monomer increased. The fluorescence quantum yields of the copolymers were significantly improved compared to the iridium complex monomer.     

Synthesis and characterization of macrocyclic polystyrene block-copolymers

The synthesis of macrocyclic polystyrene- block-poly(2-vinylpyridine) and macrocyclic polystyrene- block-poly(dimethylsiloxane) was carried out by initiation of 2-vinylpyridine (2VP) and hexamethyl-cyclotrisiloxane (D3) by difunctional living polystyryllithium followed by coupling with 1,4-bis(bromethyl)benzene (1,4-DBX) and dichloro-dimethylsilane (Cl₂SiMe₂), respectively. A small portion of the living ABA precursors were protonated to serve as isobaric linear precursors. The linear and macrocyclic block copolymers were characterized by size-exclusion chromatography (SEC). The ratios of apparent cyclic/linear SEC molecular-weight maxima versus degree of polymerization (DP) show increases with decreasing DP varying from 0.70 ± 0.03 at high DP ≤ 200 to 0.78 ± 0.044 at low DP (≥60) whereas that of the linear ABA block copolymers decreased. Increases in glass transition temperature (Tg) were also observed for the cyclic PS-b-PDMS copolymers with respect to the isobaric linear precursors. The macrocycles were characterized by ¹H and ¹³C NMR and in the case of macrocyclic PS-b-PDMS by ²⁹Si NMR as well. Broadening in the NMR absorptions of the macrocyclic block copolymers is general and is similar to that observed for the homopolymers. Differemtial scanning calorimetry (DSC) analysis of the PS-b-P2VP macrocycles shows increases in Tg at lower molecular weight as was observed for the PS and P2VP macrocycles.     

Reorganization of hydrogen-bonded block copolymer complexes

Poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers and poly(acrylic acid) (PAA) have been mixed in organic solvents. Complexation via hydrogen bonding occurs between the P4VP and PAA blocks. Those insoluble complexes aggregate to form the core of micelles surrounded by a corona of PS chains. Reorganization of these structures occurs upon addition of acidic or basic water, which results in the breaking of the hydrogen bonds between the P4VP and PAA blocks. After transfer of the initial complexes in acidic water, micelles consisting of a PS core and a protonated P4VP corona are observed. In basic water, well-defined nanoparticles formed by the PS-b-P4VP copolymers are obtained. It is demonstrated that these nanoparticles are stabilized by the negatively charged PAA chains. Finally, thermally induced disintegration of the micelles is investigated in organic solvents.     

Förster resonance energy transfer in poly(methyl methacrylates) copolymers bearing donor–acceptor 1,3‐thiazole dyes

The Förster resonance energy transfer (FRET) properties in poly(methyl methacrylate) copolymers containing 2‐(pyridine‐2‐yl) thiazole dyes were studied upon systematic variation of the donor‐to‐acceptor ratio. To this end, 2‐(pyridine‐2‐yl) thiazole dyes specially designed for the usage as energy donor and acceptor molecules were incorporated within one polymer chain. Poly(methyl methacrylate) copolymers containing these donor and acceptor dyes were synthesized using the RAFT polymerization method. Copolymers with a molar mass (M_n) of nearly 10,000 g/mol were achieved with dispersity index values (?) under 1.3. The presented copolymers act as a model system for the FRET investigation. Förster resonance energy transfer properties of the copolymers are characterized by steady state as well as time resolved fluorescence spectroscopy. The results indicate that the energy transfer rates and the transfer efficiencies are tunable by variation of the donor‐acceptor‐ratio. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4765–4773     

Antibacterial behaviour of quaternized poly(vinyl chloride)-g-poly(4-vinyl pyridine) graft copolymers

Amphiphilic graft copolymers consisting of poly(vinyl chloride)(PVC) main chains and poly(4-vinyl pyridine)(P4VP) side chains were synthesized via atom transfer radical polymerization(ATRP) using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1H-NMR). Transmission electron microscope(TEM) and small angle X-ray scattering(SAXS) analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli(E. coli), Staphylococcus aureus(S. aureus), Bacillus cereus(B. cereus), and Pseudomonas aeruginosa(P. aeruginosa) were completely killed in 24 h on the quaternized PVC-g-P4VP(46% grafting) surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.     

Dynamic mechanical properties of ionomer/ionomeric microbead composites

Composites of sulfonated polystyrene (PS-SSA) (0-8 mol % sulfonation) mixed with submicronic styrene-4 vinylpyridine (PS-4VP) (31 mol % 4VP content) microspheres were investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy, and dynamic mechanical spectroscopy at 1 Hz in the glass transition region. The resulting proton transfer reaction from the SSA to the 4VP units was confirmed by IR spectroscopy, and led to a significant increase in the post-T_g Young's modulus as well as a lengthening of the rubbery plateau. Surprisingly, the addition of sulfonated polystyrene microspheres to styrene-vinyl pyridine copolymers had no such effects, possibly because of steric factors. © 1995 John Wiley & Sons, Inc.     

Self-assembly behavior of A-B diblock and C-D random copolymer mixtures in the solution state through mediated hydrogen bonding

We have synthesized poly(methyl methacrylate- b-4-vinylpyridine) (PMMA- b-P4VP) and poly(styrene- r-vinylphenol) (PS- r-PVPh) copolymers by using anionic and free radical polymerizations, respectively. Well-defined micelles through hydrogen bonding have been prepared by mixing PMMA- b-P4VP diblock copolymer and PS- r-PVPh random copolymer in a single solvent. Block copolymers were mixed with random copolymers, with various [N]/[OH] ratios (4/1, 2/1, 1/1, and 1/4) in which "[N]/[OH]" represents the molar ratio of pyridine groups on P4VP to hydroxyl groups on PVPh. The presence distribution of PVPh/P4VP and PVPh/PMMA hydrogen bonding depends on the feeding ratio of PVPh to P4VP. When the PVPh content is lower than that of P4VP, hydrogen bonding occurs only between PVPh and P4VP; with excess PVPh, additional hydrogen bonding between PVPh and PMMA would occur. Furthermore, the effect of the solvent quality on the self-assembly behavior of PMMA- b-P4VP/PS- r-PVPh blends is investigated by considering tetrahydrofuran (THF) and dimethylformamide (DMF) as common solvents. We can mediate the strength of hydrogen bonding in blend systems by adopting different solvents and inducing different morphology transitions.