Dendronized supramolecular polymers self‐assembled from dendritic ionic liquids

The synthesis, structural, and retrostructural analysis of a library of self‐assembling dendrons containing triethyl and tripropyl ammonium, pyridinium and 3‐methylimidazolium chloride, tetrafluoroborate, and hexafluorophosphate at their apex are reported. These dendritic ionic liquids self‐assemble into supramolecular columns or spheres which self‐organize into 2D hexagonal or rectangular and 3D cubic or tetragonal liquid crystalline and crystalline lattices. Structural analysis by X‐ray diffraction experiments demonstrated the self‐assembly of supramolecular dendrimers containing columnar and spherical nanoscale ionic liquid reactors segregated in their core. Both in the supramolecular columns and spheres the noncovalent interactions mediated by the ionic liquid provide a supramolecular polymer and therefore, these assemblies represent a new class of dendronized supramolecular polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4165–4193, 2009     

Linear‐dendritic block copolymer hosts for the encapsulation of electro‐optic chromophores via H‐Bonding

Linear‐dendritic block copolymer hosts were synthesized by end‐functionalizing poly(methylmethacrylate) with dendrons that acted as hydrogen‐bonding acceptors for nonlinear optical chromophores. Second harmonic generation experiments indicate that the d₃₃ coefficients and maximum chromophore loading are increased in linear‐dendritic block copolymer hosts over comparable homopolymer hosts. Transmission electron microscopy shows 5–10 nm chromophore domains, confirming the effective spatial dispersion of the chromophores. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5017–5026, 2009     

Fluorene‐based materials and their supramolecular properties

Fluorene‐based π‐conjugated polymers and oligomers combine several advantageous properties that make them well‐suited candidates for applications in organic optoelectronic devices and chemical sensors. This review highlights strategies to synthesize these materials and to tune their absorption and emission colors. Furthermore, methods to control their supramolecular organization will be discussed. In many cases, a delicate interplay between the chemical structure and the processing conditions are found, resulting in a high sensitivity of both structural features and optical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4215–4233, 2009     

Self‐assembled anionic micellar template for polypyrrole,polyaniline, and their random copolymer nanomaterials

We report an anionic surfactant approach for size and shape control in polyaniline, polypyrrole, and their polyaniline‐co‐polypyrrole random copolymer nanomaterials. A renewable resource azobenzenesulfonic acid anionic surfactant was developed for template‐assisted synthesis of these classes of nanomaterials. The surfactant exists as 4.3 nm micelle in water and self‐organizes with pyrrole to produce spherical aggregates. The sizes of the spherical aggregates were controlled by water dilution and subsequent oxidation of these templates, produced polypyrrole nanospheres of 0.5 μM to 50 nm dimensions. The anionic surfactant interacts differently with aniline and forms cylindrical aggregates, which exclusively produce nanofibers of ∼180 nm in diameter with length up to 3–5 μM. The template selectivity of surfactant toward aniline and pyrrole was used to tune the nanostructure of the aniline‐pyrrole random copolymers from nanofiber‐to‐nanorod‐to‐nanospheres. Dynamic light scattering technique and electron microscopes were used to study the mechanistic aspects of the template‐assisted polymerization. The four probe conductivity of the copolymers showed a nonlinear trend and the conductivity passes through minimum at 60–80% of pyrrole in the feed. The amphiphilic dopant effectively penetrates into the crystal lattices of the polymer chain and induces high solid state ordering in the homopolymer nanomaterials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 830–846, 2009     

Synthesis and thermal characterization of poly(dimethyl bicyclobutane‐1,3‐dicarboxylate) and its copolymers

Dimethyl bicyclobutane‐1,3‐dicarboxylate was synthesized. Its homopolymer (PDBD) containing exclusively cyclobutane rings in its backbone was prepared by free radical polymerization. The copolymers of this bicyclobutane monomer with methyl methacrylate were also prepared. The glass transition temperature of the homopolymer is 159°C, while those of its copolymers are 143 and 121°C with 75/25 and 50/50 of the P(DBD/MMA) composition ratio, respectively. The T_g of PDBD homopolymer is substantially higher than that of commercial PMMA homopolymer despite a lower molecular weight, and is also much higher than that of its monomethyl cyclobutanecarboxylate analogue. These DBD homopolymer and copolymers also show better thermostability than the PMMA homopolymer. The weight‐average molecular weight of homopolymer is 37,000. The polydispersities of these polymers are relatively narrow, with the range of 1.6–1.9. These polymers form clear colorless films resembling PMMA film. The DBD homopolymer film shows a very similar optical cutoff compared to PMMA. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1569–1575, 1999     

RAFT polymerization of a novel activated ester monomer and conversion to a terpyridine‐containing homopolymer

Developing new materials with unique properties for nanotechnology applications, in general, and supramolecular polymers, in particular, lie at the heart of much ongoing research. In line with these efforts, we have been exploring polymers containing terpyridine (terpy) in the side chain. Here we report a new monomer that effectively undergoes reversible addition fragmentation chain transfer polymerization (RAFT) to yield high‐molecular‐weight (M_n) polymers with narrow polydispersity (PDI). The monomer is an N‐succinimide activated ester of p‐vinyl benzoic acid. Under RAFT conditions, poly(N‐succinimide p‐vinylbenzoate)s were generated, with M_n ranging between 44 and 61 kDa and PDI of 1.03–1.07. One of these homopolymers was reacted with an amine functionalized terpy, creating a new homopolymer containing terpy ligands on every monomer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5618–5625, 2007     

Latent solid‐phase extraction with thermoresponsive soluble polymers

The use of soluble thermoresponsive polymers to sequester or scavenge hydrophobic guest molecules from dilute aqueous solutions on heating is described. In these studies, a homopolymer of N‐isopropylacrylamide was shown to sequester 46–83% of a soluble monochlorotriazine from 0.1–10 ppm aqueous solutions when heating above this polymer's lower critical solution temperature (LCST). Substitution of the reactive piperidine‐containing 20:1 copolymer poly(N‐isopropylacrylamide)‐c‐poly[N‐4‐(acrylamidomethyl)piperidine] for this unreactive polymer led to >98% scavenging of these same triazines when heating above this reactive polymer's LCST. The monochlorotriazine guests studied included the herbicide atrazine and two dye‐labeled analogues of this herbicide. In one case, an atrazine analogue was designed so as to contain a dansyl group for fluorescence analysis. In the second case, an atrazine analogue was labeled with a methyl red group to facilitate visual and spectrophotometric analysis. Atrazine concentrations were measured with liquid chromatography–mass spectrometry. The enhanced efficiency of the reactive piperidine‐containing copolymer scavenger in removing triazines from solution is attributed to covalent bond formation by nucleophilic aromatic substitution of the chlorine of the monochlorotriazines by the piperidine nucleophile on the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6309–6317, 2004     

Effects of solvent,casting temperature,and guest/host stoichiometries on the properties of shape memory material based on partial α‐CD‐PEG inclusion complex

A series of supramolecular inclusion complex (IC) films were formed by threading α‐cyclodextrin (α‐CD) molecules over poly(ethylene glycol) (PEG), according to the designed ratio of α‐CD/PEG. Because of containing α‐CD‐PEG inclusion crystallites as physical crosslinks and uncovered PEG crystallites as “switch phase”, the resulting supramolecular α‐CD‐PEG partial ICs displayed a shape memory effect. The properties of the materials were investigated by ¹H‐NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling measurement. It was found that the casting temperature, solvent, and the ratio of α‐CD‐PEG inclusion/PEG had great influence on the formation and properties of α‐CD‐PEG partial ICs. The modes of complexes on different conditions were proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 951–957, 2010     

Surface modification of gold nanoparticles with polyhedral oligomeric silsesquioxane and incorporation within polymer matrices

A new approach to achieve polymer‐mediated gold ferromagnetic nanocomposites in a polyhedral oligomeric silsesquioxane (POSS)‐containing random copolymer matrix has been developed. Stable and narrow distributed gold nanoparticles modified by 3‐mercaptopropylisobutyl POSS to form Au‐POSS nanoparticles are prepared by two‐phase liquid‐liquid method. These Au‐POSS nanoparticles form partial particle aggregation by blending with poly(n‐butyl methacrylate) (PnBMA) homopolymer because of poor miscibility between Au‐POSS and PnBMA polymer matrix. The incorporation the POSS moiety into the PnBMA main chain as a random copolymer matrix displays well‐dispersed gold nanoparticles because the POSS‐POSS interaction enhances miscibility between gold nanoparticles and the PnBMA‐POSS copolymer matrix. This gold‐containing nanocomposite exhibits ferromagnetic phenomenon at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 811–819, 2009     

A novel route to in‐situ incorporation of silver nanoparticles into supramolecular hydrogel networks

A novel strategy was developed for the in situ incorporation of silver nanoparticles into the supramolecular hydrogel networks, in which colloidally stable silver hydrosols were firstly prepared in the presence of an amphiphilic block copolymer of poly(oxyethylene)‐poly(oxypropylene)‐poly(oxyethylene) and then mixed with aqueous solution of α‐cyclodextrin. The analyses from rheology, X‐ray diffraction, and scanning electron microscopy confirmed the formation of the supramolecular‐structured hydrogels hybridized with silver nanoparticles. In particular, the colloidal stability of the resultant silver hydrosol and its gelation kinetics in the presence of α‐cyclodextrin as well as the viscoelastic properties of the resultant hybrid hydrogel were investigated under various concentrations of the used block copolymer. It was found that the used block copolymer could act not only as the effective reducing and stabilizing agents for the preparation of the silver hydrosol but also as the effective guest molecule for the supramolecular self‐assembly with α‐cyclodextrin. In addition, the effects of silver nanoparticles on the gelation process and the hydrogel strength were also studied. Such a hybrid hydrogel material could show a good catalytic activity for the reduction of methylene blue dye by sodium borohydride. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 740–749, 2009     

Control of thermoresponsive property of urea end‐functionalized poly(N‐isopropylacrylamide) based on the hydrogen bond‐assisted self‐assembly in water

The precise synthesis and variation in the thermoresponsive property based on the supramolecular assembly of a novel urea end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) were studied. A series of PNIPAMs with different diphenylurea groups at the chain end (X? Ph? NH? CO? NH? Ph? trz? PNIPAM: X = H, OCH₃, CH₃, NO₂, Cl, and CF₃) were synthesized by using a combination of the atom transfer radical polymerization and the copper(I)‐catalyzed azide‐alkyne cycloaddition. The cloud point of the obtained polymers depended on the hydrogen‐bonding ability of the introduced urea group. The ¹H NMR measurement suggested that the obtained PNIPAM assembled in water via the intermolecular hydrogen bonding by the terminal urea group. From the dynamic light scattering and transmission electron microscopy measurements, the aggregated nanoparticles of the resulting polymer were directly observed in water at a temperature below its cloud point. The hydrogen‐bonding property of the chain end urea group was concluded to be involved in the aggregation of the PNIPAM in water, leading to the variation in its cloud point. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6259–6268, 2009     

Main‐chain,thermotropic, liquid‐crystalline,hydrogen‐bonded polymers of 4,4′‐bipyridyl with aliphatic dicarboxylic acids

A series of main‐chain, thermotropic, liquid‐crystalline (LC), hydrogen‐bonded polymers or self‐assembled structures based on 4,4′‐bipyridyl as a hydrogen‐bond acceptor and aliphatic dicarboxylic acids, such as adipic and sebacic acids, as hydrogen‐bond donors were prepared by a slow evaporation technique from a pyridine solution and were characterized for their thermotropic, LC properties with a number of experimental techniques. The homopolymer of 4,4′‐bipyridyl with adipic acid exhibited high‐order and low‐order smectic phases, and that with sebacic acid exhibited only a high‐order smectic phase. Like the homopolymer with adipic acid, the two copolymers of 4,4′‐bipyridyl with adipic and sebacic acids (75/25 and 25/75) also exhibited two types of smectic phases. In contrast, the copolymer of 4,4′‐bipyridyl with adipic and sebacic acids (50/50), like the homopolymer with sebacic acid, exhibited only one high‐order smectic phase. Each of them, including the copolymers, had a broad temperature range of LC phases (36–51 °C). The effect of copolymerization for these hydrogen‐bonded polymers on the thermotropic properties was examined. Generally, copolymerization increased the temperature range of LC phases for these polymers, as expected, with a larger decrease in the crystal‐to‐LC transition than in the LC‐to‐isotropic transition. Additionally, it neither suppressed the formation of smectic phases nor promoted the formation of a nematic phase in these hydrogen‐bonded polymers, as usually observed in many thermotropic LC polymers. The thermal transitions for all of them, measured by differential scanning calorimetry, were well below their decomposition temperatures, as measured by thermogravimetric analysis, which were in the temperature range of 193–210 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1282–1295, 2003     

Sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions as a route to well‐defined mono and bis end‐functionalized poly(N‐isopropylacrylamide)

Sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions have been used as a facile and quantitative method for modifying end‐groups on an N‐isopropylacrylamide (NIPAm) homopolymer. A well‐defined precursor of polyNIPAm (PNIPAm) was prepared via reversible addition‐fragmentation chain transfer (RAFT) polymerization in DMF at 70 °C using the 1‐cyano‐1‐methylethyl dithiobenzoate/2,2′‐azobis(2‐methylpropionitrile) chain transfer agent/initiator combination yielding a homopolymer with an absolute molecular weight of 5880 and polydispersity index of 1.18. The dithiobenzoate end‐groups were modified in a one‐pot process via primary amine cleavage followed by phosphine‐mediated nucleophilic thiol‐ene click reactions with either allyl methacrylate or propargyl acrylate yielding ene and yne terminal PNIPAm homopolymers quantitatively. The ene and yne groups were then modified, quantitatively as determined by ¹H NMR spectroscopy, via radical thiol‐ene and radical thiol‐yne reactions with three representative commercially available thiols yielding the mono and bis end functional NIPAm homopolymers. This is the first time such sequential thiol‐ene/thiol‐ene and thiol‐ene/thiol‐yne reactions have been used in polymer synthesis/end‐group modification. The lower critical solution temperatures (LCST) were then determined for all PNIPAm homopolymers using a combination of optical measurements and dynamic light scattering. It is shown that the LCST varies depending on the chemical nature of the end‐groups with measured values lying in the range 26–35 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3544–3557, 2009     

Synthesis and light‐emitting properties of carbazole‐based copolymers bearing cyano‐substituted arylenevinylene chromophore

Two arylenevinylene compounds bearing the cyano group at α‐position ( 6 ) and β‐position ( 9 ) from the dialkoxylphenylene unit were synthesized, in which the molecular termini were functionalized with 3‐bromocarbazole. The Suzuki coupling copolymerization of these compounds with 1,4‐bis[(3′‐bromocarbazole‐9′‐yl)methylene]‐2,5‐didecyloxybenzene and 9,9‐dihexylfluorene‐2,7‐bis(boronic acid) was carried out to obtain copolymers ( cp67 and cp97 ) containing the cyano‐substituted arylenevinylene fluorophore of 7 mol %. Model compounds ( 6 ′ and 9 ′) corresponding to the arylenevinylene fluorophore were also prepared. The UV spectra of copolymers resembled that of homopolymer hp with no arylenevinylene segment in both CHCl₃ solution and thin film. The emission maxima of copolymers in CHCl₃ (394 nm) agreed with that of homopolymer indicating that the emission bands originated from the carbazole‐fluorene‐carbazole segment. The emission maximum wavelength of copolymer cp67 in thin film (477 nm) indicated fluorescence from the cyano‐substituted arylenevinylene fluorophore because of the occurrence of fluorescence resonance electron transfer. In contrast, copolymer cp97 showed fluorescence at 528 nm to suggest the formation of a new emissive species such as a charge‐transfer complex (exciplex). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 91–98, 2010     

Synthesis and characterization of physical crosslinking systems based on cyclodextrin inclusion/host‐guest complexation

New supramolecular assemblies based on cyclodextrin and adamantane were prepared. Two methacrylate monomers bearing cyclodextrin and adamantane were synthesized, and copolymerized with poly(ethylene glycol) methyl ether methacrylate, (PEGMA, 300 g/mol), by free radical polymerization. Copolymers bearing pendent cyclodextrin and adamantane were characterized by NMR, FTIR, TGA, SEC, Differential scanning calorimetry (DSC), and UV‐visible spectrophotometer. All copolymers showed two distinct glass transitions. The specific interaction between pendent adamantyl and cyclodextrin was examined by ¹H‐NMR. The viscoelastic properties of supramolecular assemblies were investigated with frequency and temperature sweep experiments. The specific host‐guest interaction between pendent adamantyl and cyclodextrin lead to large increases of the viscosity; and depending on the concentration of these groups, also to gel formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 581–592, 2010     

Polycarbazoles via C?N coupling reactions of phthaloyl bis‐9H‐carbazoles with activated difluorides

1,3‐Phthaloyl bis‐9H‐carbazole (MPC) and 1,4‐phthaloyl bis‐9H‐carbazole (PPC) were synthesized by a Friedel‐Crafts reaction of carbazole with terephthaloyl chloride or isophthaloyl chloride. Homopolymers were obtained by a C? N coupling reaction with activated difluorides and copolymers were synthesized with 4,4′‐biphenol as a comonomer by a nucleophilic substitution reaction between these NH‐ and OH‐containing monomers and the activated difluoro monomers. The inherent viscosities of the polymers ranged from 0.35 to 1.03 dL/g. These polymers exhibited glass‐transition temperatures greater than 238 °C with the PPC‐containing homopolymer showing the highest value, 326.4 °C. The thermal stabilities indicated no significant weight loss below 450 °C and the temperatures of 5% weight loss ranged from 514.0 to 546.3 °C. The polymers showed reasonable solubility in organic solvents such as DMAC, DMSO, and NMP. UV absorption and fluorescence emission properties are presented. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4326–4331, 2009     

Synthesis of stimuli‐responsive macroazoinitiators and their use as an inistab toward hairy polymer latex particles

Stimuli‐responsive macroazoinitiators with central azo unit have been synthesized by atom transfer radical polymerization (ATRP) of 2‐(dimethylamino)ethyl methacrylate or 2‐(diethylamino)ethyl methacrylate in 2‐propanol at 25 °C. The mean degree of polymerization of the polymer chains besides the azo group was fixed between 25 and 60. ¹H NMR, gel permeation chromatography, UV‐Vis spectrophotometer, and surface tensiometer were used to characterize the stimuli‐responsive macroazoinitiators in terms of their chemical structure, molecular weight, polydispersity, and pH‐responsive behavior, respectively. Eventually, dispersion polymerization of styrene using the poly[2‐(diethylamino)ethyl methacrylate] (PDEA) macroazoinitiator as an inistab (initiator + stabilizer) in 2‐propanol medium was conducted. Near‐monodisperse 98 nm polystyrene (PS) latex particles with pH‐responsive PDEA hair were successfully synthesized. The PS latex particles with the PDEA hair can be dispersed in acidic aqueous media where the PDEA hair was protonated and was solvated, and can be flocculated in basic aqueous media where the PDEA hair was deprotonated and was precipitated. This dispersion‐flocculation cycle was reversible. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3431–3443, 2009     

Prepolymerization and postpolymerization functionalization approaches to fluorescent conjugated carbazole‐based glycopolymers via “click chemistry”

Facile prepolymerization and postpolymerization functionalization approaches to prepare well‐defined fluorescent conjugated glycopolymers through Cu(I)‐catalyzed azide/alkyne “Click” ligation were explored. Two well‐defined carbazole‐based fluorescent conjugated glycopolymers were readily synthesized based on these strategies and characterized by ¹H NMR, ¹³C NMR, IR spectra, and UV‐vis spectra. The “Click” ligation offers a very effective conjugation method to covalently attach carbohydrate residues to fluorescent conjugated polymers. In addition, the studies of carbohydrate–lectin interactions were performed by titration of concanavalin A (Con A) to D ‐glucose‐bearing poly(anthracene‐alt‐carbazole) copolymer P‐2 resulting in significant fluorescence quenching of the polymer due to carbohydrate–lectin interactions. When peanut agglutinin (PNA) was added, no distinct change in the fluorescent properties of P‐2 was observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2948–2957, 2009     

Structural design of stimuli‐responsive bioconjugated hydrogels that respond to a target antigen

Stimuli‐responsive bioconjugated hydrogels that can respond to a target antigen (antigen‐responsive hydrogels) were prepared by introducing antigen‐antibody bindings as reversible crosslinks into the gel networks. The preparation conditions of the antigen‐responsive hydrogels and the mechanism of the antigen‐responsive behavior were investigated, focusing on bioconjugated hydrogel structures. This article also focuses on the effect of semi‐interpenetrating polymer network (semi‐IPN) structures on the antigen‐responsive swelling/shrinking behavior of bioconjugated hydrogels with antigen‐antibody bindings. The preparation conditions and the network structures of the bioconjugated hydrogels are discussed in relation to designing antigen‐responsive hydrogels. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2144–2157, 2009     

Matrix‐assisted laser desorption/ionization time‐of‐flight analysis of the copolymerization reaction of an expanding monomer with a diepoxide

In search of a composite with low stress and low shrinkage properties, this study includes matrix‐assisted laser desorption/ionization time‐of‐flight analysis of the photoinitiated cationic polymerization between an expanding monomer [1,5,7,11‐tetraoxaspiro[5.5]undecane (TOSU)] and a diepoxide [bisphenol A diglycidyl ether (BADGE)]. Past studies using NMR and differential scanning calorimetry analyses concluded copolymerization indirectly on the basis of deviations from homopolymer product data. This is the first study to provide direct evidence of copolymerization between these species. Unlike previous research, this study enables the identification of the TOSU homopolymer and the absence of the BADGE homopolymer, suggesting initial cationic activation of TOSU. In addition to peaks that correspond to the presumed mechanism for six‐membered TOSU polymerization, many peaks have a net gain or loss of cyclic carbonate in support of a new polymerization mechanism participating in the reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5962–5970, 2005