Charge mosaic membrane with a microstructure of poly(styrene-b-4-vinylpyridine)

Well defined AB and BAB type poly[styrene(ST)-b-4-vinylpyridine(4VP)]s were prepared by anionic living polymerization in tetrahydrofuran (THF) at ?78°C. Casting AB and BAB type poly(ST-b-4VP)s with a composition of about 50 mol% PST from 1,1,2-trichloroethane (TCE) produced specimens with lamellar microdomain structures. Quaternization of P4VP and sulfonation of PST domains (lamellar and spherical structures), accompanied by each domain fixing, were carried out under various reaction conditions. The piezodialysis of the prepared charge mosaic membrane with its lamellar microdomain structure was measured from a sodium chloride (NaCl) aqueous solution. The results are discussed in some detail.     

Synthesis of poly(styrene-tetrahydrofuran-2-methyl-2-oxazoline) triblock and graft copolymers

Poly[styrene (ST)-tetrahydrofuran (THF)-2-methyl-2-oxazoline(MeOz)] triblock and graft copolymers were prepared by ionic polymerizations. Poly(ST-THF) graft copolymers were synthesized by coupling of ST-4-vinylpyridine (4VP) copolymer with a large excess of PTHF dication. The ion coupling of PST dianion with PTHF dication was accompanied by the side reaction (abstraction of α proton of oxonium ion). After tosylation of terminal hydroxyl groups of PTHF blocks, cationic copolymerizations of MeOz with poly(ST-THF) block and graft copolymers were carried out, and characteristics of produced copolymers were investigated in some detail.     

Novel styrene-butadiene block copolymers by sequential and statistical copolymerization of corresponding macromonomers

This paper concerns the synthesis of two different structures of styrene-butadiene block copolymers that were respectively obtained via sequential and statistical ring-opening metathesis copolymerization of norbornene-terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene-butadiene copolymers originates from the observation that phase-separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (χ), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two types of copolymers -prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively- exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.     

Synthesis and characterization of chitosan-graft-polycaprolactone copolymers

The graft copolymers of chitosan with polycaprolactone (PCL) were prepared through a protection-graft-deprotection route using phthaloylchitosan as intermediate. PCL macromonomers terminated with isocyanate groups reacted with hydroxyl groups of phthaloyl-protected chitosan regioselectively, and then phthaloyl groups were deprotected to give the free amino groups. The graft reaction was carried out in homogeneous system and yielded copolymers with high grafting content due to solubilization. FTIR, NMR and XRD were detected to characterize the resultant chitosan-graft-PCL copolymers.     

Multisensitive polymers based on 2‐vinylpyridine and N‐isopropylacrylamide *

Poly(2‐vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl‐mediated radical polymerization with a hydroxy‐functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free‐radical copolymerization of these macromonomers with N‐isopropylacrylamide gave a graft copolymer with a poly(N‐ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797–3804, 2001     

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.     

Water-soluble graft copolymers from macromonomer method

Water-soluble graft copolymers of well-defined structure having hydrophobic polymethacrylate branches with different ester groups were prepared by the macromonomer method. Methacrylate macromonomers of controlled molecular weights having a methacryloyloxyl end group were synthesized by radical polymerization of the corresponding monomer in the presence of thioglycolic acid followed by the reaction of glycidyl methacrylate with the terminal carboxyl group. These macromonomers were copolymerized with methacrylic acid and methyl methacrylate to prepare tailor-made graft copolymers composed of a hydrophlic backbone and different kinds of hydrophobic branches, which were characterized by elemental analysis, NMR, and GPC. The viscosities of the aqueous solutions of the sodium salts of these graft copolymers were measured. It was found that the viscosity of the dilute solution of the graft copolymer was remarkably high compared with the corresponding random copolymer irrespective of the ester group in branch segments. Solubilizing behavior of Orange-OT in aqueous solutions of the graft copolymers and the random copolymer were also investigated to study the nature of the hydrophobic domain of the graft copolymers.     

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.     

Wholly aromatic polyamides by the direct polycondensation reaction using triphenyl phosphite in the presence of poly(4-vinylpyridine)

The polycondensation reaction of aromatic dicarboxylic acids and diamines by using triphenyl phosphite were carried out in N-methylpyrrolidone (NMP) in the presence of poly(4-vinylpyridine) (P4VP). The reaction, especially of terephthalic acid (TPA), was markedly facilitated to give the absence of P4VP. The reaction promoted by P4VP was further favored by the addition of various pyridine derivatives; of the pyridines examined, pyridine was most effective, giving the best results at a high level (pyridine/P4VP values up to 26). P4VP of the molecular weight in the range of 1.3 × 10⁴?3.0 × 10⁵ did not affect the viscosity of the resulting polymer. These favorable additive effects of P4VP on the reaction of TPA were not observed in the reactions of isophthalic acid, and m -and p-aminobenzoic acids.     

Investigation of Hydrogen Bonded Interpolymer Complexes Based on Poly (n-butyl methacrylate–co-methacrylic acid) and Poly (n-butyl methacrylate -co-4-vinyl pyridine). Temperature Effect

Summary: Two kinds of interpolymer complexes as soluble or precipitate of different structures were obtained in both THF and butan-2-one as common solvents by monitoring the hydrogen-bonding density within homoblends of poly(n-butyl methacrylate-co-4-vinylpyridine) (BM4VP) and poly(n-butyl methacrylate-co-methacrylic acid) (BMMA). A viscometry study confirmed such differences between these two types of interpolymer complexes from the behavior of the reduced viscosity of their blend solutions with feed blend composition. Qualitative and quantitative analyses of the interactions that occurred between these copolymers of relatively bulky side chain length containing various amounts of methacrylic acid and 4-vinylpyridine were carried out by FTIR. The fraction of associated pyridine groups to the carboxylic groups of the BMMA increases as the content of these latter increases in the BMMA/BM4VP blends. The obtained results also showed that the fractions of associated pyridine within the BMMA25/BM4VP26 blends are higher than those within BMMA18/BM4VP19 or BMMA8/BM4VP10. The FTIR analysis of a selected BMMA18/BM4VP19 1:1 ratio, carried out from 80 °C to 160 °C, above the glass transition temperatures of the two constituents of the blend, confirms the presence of strong hydrogen bonding interactions between the pyridine and the carboxylic groups within these blends even at 160 °C. A LCST is expected to occur at higher temperature as shown from the progressive decrease of the fraction of the associated pyridine.     

Hydrogen bond mediated supramolecular micellization of diblock copolymer mixture in common solvents

We report a new approach toward preparing self-assembled hydrogen-bonded complexes having vesicle and patched spherical structures from two species of block copolymers in nonselective solvents. Two diblock copolymers, poly(styrene-b-vinyl phenol) (PS-b-PVPh) and poly(methyl methacrylate-b-4-vinylpyridine) (PMMA-b-P4VP), were synthesized through anionic polymerization. The assembly of vesicles from the intermolecular complex formed after mixing PS-b-PVPH with PMMA-b-P4VP in THF was driven by strong hydrogen bonding between the complementary binding sites on the PVPH and P4VP blocks. In contrast, well-defined patched spherical micelles formed after blending PS-b-PVPh with PMMA-b-P4VP in DMF: the weaker hydrogen bonds formed between the PVPh and P4VP blocks in DMF, relative to those in THF, resulted in the formation of spherical micelles having compartmentalized coronas consisting of PS and PMMA blocks.     

Synthesis of macromonomers of acrylic acid by telomerization: Application to the synthesis of polystyrene‐g‐poly(acrylic acid) copolymers

The synthesis of macromonomers of acrylic acid was performed by telomerization in a three‐step process. The first step was the telomerization of tert‐butyl acrylate in the presence of thioglycolic acid. Different molecular weights were obtained with different ratios of the monomer to the transfer agent. Good control of the molecular weights and architectures of the oligomers (e.g., the presence of an acid function on the chain end) was observed. The transfer constant of tert‐butyl acrylate with thioglycolic acid was assessed (chain‐transfer constant = 0.6). In the second step, the terminal unsaturation of the oligomers was obtained by the reaction of the terminal acid groups with 2‐isocyanatoethyl methacrylate to yield the macromonomers of tert‐butyl acrylate. In the last step, the tert‐butyl acrylate groups were hydrolyzed in the presence of trifluoroacetic acid at room temperature. The macromonomers were copolymerized with styrene to obtain graft copolymers, and the reactivity ratios were evaluated. Finally, the copolymers were characterized with surface electron microscopy and atom force microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 395–415, 2007     

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.

Complex micelles formed from two diblock copolymers for applications in controlled drug release

Double‐responsive core‐shell‐corona complex micelles for applications in drug release were formed from self‐assembly of two diblock copolymers PtBA‐b‐ PNIPAM and PtBA‐b‐P4VP. The two diblock copolymers coaggregated into core‐shell complex micelles in acidic water with the hydrophobic PtBA blocks as the common core and soluble PNIPAM/P4VP blocks as the mixed shell. Increasing temperature or pH value, the micelles converted into core‐shell‐corona micelles because of the collapse of PNIPAM or P4VP blocks as the inner shell and soluble P4VP or PNIPAM chains stretching outside as the outer corona. The anti‐inflammation drug naproxen (NAP) was loaded as the model drug in micelles in acidic water and released because of the ionization of NAP in alkaline solutions. Compared with pure core‐shell micelles, release of NAP from core‐shell‐corona complex micelles avoided the burst diffusion and the release rate is more easily controlled by tuning the composition of the mixtures or by adjusting the pH of the medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1804–1810, 2009     

Influence of a liquid crystalline block on the microdomain structure of block copolymers

We report on the phase behavior and microdomain structure of two types of diblock copolymers containing a liquid crystal (LC) block joined to a flexible coil block. Consideration of the symmetry groups of the liquid crystalline phases and of the block copolymer microdomain structures provides a rationale for predicting the possible types of liquid crystalline block copolymer morphologies. Both previously reported and newly discovered structural types are identified. Possible organizational schemes are developed for the mesogens and periodic disclination defects with respect to the intermaterial dividing surfaces separating the liquid crystalline and flexible coil domains. The first type of copolymer investigated has a rod-like LC block whereas the second type copolymer has a side chain LC block. Five different rod-coil diblocks based on poly(hexyl isocyanate-b-styrene) P(HIC-b-S) were synthesized by anionic polymerization. Wavy lamellae, zig-zag and arrowhead microdomain morphologies corresponding to smectic-C and smectic-O structures were observed depending on the composition. These layered phases have the director (PHIC chain axis) tilted at various orientations with respect to the layer normal. Side-chain LC diblocks based on functionalized poly(isoprene-b-styrene) P(I-b-S) were also investigated. These polymers were synthesized using polymer analogous chemistry from P(I-b-S) precursors. Three different mesogenic groups were attached to the PI blocks: one based on biphenyl benzoate and two based on azobenzene. The microdomain structures found for the functionalized poly(isoprene side-chain LC-b-styrene) P(ILC-b-S) diblocks are typical of traditional coil-coil diblocks (lamellae and cylinders). However, these morphologies possess an additional smectic layering of the mesogens within the microdomains of the LC block. In the case of the rod-coil diblocks, the transformation from an initially isotropic state to the final microphase separated solid state occurs via nematic and then smectic liquid crystalline states, whereas for the side-chain LC-coil cases, the microphase separation transition occurs prior to development of orientational order. The long-range microdomain order of LC block-coil block copolymers can extend over very large distances due to the influence of the orientational ordering of the LC block.     

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.     

Controlled sulfonation of poly(arylene ether sulfone)s and poly(arylene ether ketone)s with different molecular structures for polymer electrolyte membranes

Poly(arylene ether sulfone) copolymers derived from 9,9-bis(4-hydroxyphenyl)fluorene, bisphenol S and 4,4′-difluorodiphenylsulfone and poly(arylene ether ketone) copolymers derived from 4-phenoxybiphenyl, diphenyl ether and isophthaloyl chloride were prepared as precursor polymers for sulfonation reaction in which sulfonic groups are introduced quantitatively into specified positions. Sulfonation reaction for these two series of copolymers by concentrated sulfuric acid was successfully carried out to give sulfonated polymers with controlled positions and degree of sulfonation. Thermal stability, moisture absorption and proton conductivity for these two series of copolymers were measured and the results were compared to those of perfluorosulfonic acid polymers.     

A macromonomer approach to the synthesis of poly(1,1‐bis(ethoxycarbonyl)‐2‐vinyl cyclopropane‐graft‐dimethyl siloxane)

Poly(1,1‐bis(ethoxycarbonyl)‐2‐vinyl cyclopropane (ECVP)‐graft‐dimethyl siloxane) copolymers were prepared using a macromonomer approach. Poly(dimethyl siloxane) (PDMS) macromonomers were prepared by living anionic polymerization of cyclosiloxanes followed by sequential chain‐end capping with allyl chloroformate. These macromonomers were then copolymerized with ECVP. MALDI‐ToF mass spectrometry and ¹H NMR spectroscopy were used to show that the macromonomers had approximately 80% of the end groups functionalized with allyl carbonate groups. Gradient polymer elution chromatography showed that high yields of the graft copolymers were obtained, along with only small fractions of the PECVP and PDMS homopolymers. Differential scanning calorimetry showed that the low glass transition temperature (T_g) of the PDMS component could be maintained in the graft copolymers. However, the T_g was a function of polymer composition and the polymers produced had T_gs that ranged from ?50 to ?120 °C. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of well-defined all-acrylic graft copolymers

Well defined all-acrylic graft copolymers have been synthesized using the macromonomer technique. Poly(methyl methacrylate) (PMMA) macromonomers of controlled molecular weight and narrow molecular weight distribution have been synthesized by group transfer polymerization (GTP) using a protected hydroxyl functional initiator. These macromonomers were quantitatively functionalized with a polymerizable acrylic and group and copolymerized under free radical conditions with 2-ethylhexyl acrylate (2EHA) to form the desired well defined graft copolymers in high yields. The macromonomers and the copolymers have been characterized by a variety of spectroscopic, chromatographic and thermal analysis methods. Transparent, multiphase materials with glass transition temperature (Tg) values of approximately -65 °C and 115 °C were obtained. The reaction conditions necessary to generate these materials most effectively have also been investigated and are described herein.     

Synthesis of cross-linked core-shell polymer particles by free-radical dispersion copolymerization of 4-vinylpyridine with polystyrene macromonomers in nonaqueous media

Cross-linked core-shell polymer particles were synthesized by free-radical dispersion copolymerization of 4-vinylpyridine (4VP) and various kinds of cross-linking reagents with methacryloyl-terminated polystyrene (PS) macromonomers in nonaqueous media such as 1,4-dioxane and cyclohexane. Well-defined particles were obtained by copolymerization of 4VP with ethylene glycol dimethacrylate (EGDM) in a dioxane medium. The particle diameters (D(n)=40-990 nm) decreased drastically both with increasing the feed concentration ratio of macromonomer to 4VP, [PS-M]/[4VP], and with increasing molecular weight of PS-M macromonomers. The particle size distribution (D(w)/D(n)) was in the range 1.02-1.10. PS-M macromonomers acted not only as comonomers but also as stabilizers. The particle diameters obtained in dioxane were smaller than those obtained in cyclohexane. Thus, we observed a tendency to smaller particle size as the media became more soluble for PS-M macromonomer.