Supramolecular self-assembly of block copolymer based on rigid surfactant

The supramolecular self-assembling of pyridine-containing amphiphilic block copolymers (PS-b- P4VP and PS-PI-P2VP) and 4-biphenylcarboxylic acid (BPCA) in selective solvents has been systematically studied. BPCA molecules are able to complex with the vinylpyridine (VP) moieties through hydrogen bonding, which leads to a transformation of spherical block copolymer micelles into structured nanofibers in solutions. The effects of molar ratio of BPCA to the VP repeat units, solvent selectivity, and copolymer composition on the supramolecular complex nanofiber formation have been systematically investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The formation mechanism of supramolecular self-assembly nanofibers was discussed.     

Photo-crosslinking and negative-type micropattern formation of a polymeric photobase generator containing phthalimido carbamate groups

The photo-crosslinking reaction of a polymeric photobase generator containing phthalimido carbamate (PC) groups was studied and applied to the formation of a negative type micropattern. The copolymer containing PC groups was prepared through the polymerization of methyl methacrylate and phthalimido methacryloxyethylcarbamate (PMC). The photochemical and cross-linking reaction of the copolymer film were studied using the UV and IR absorption spectral changes along with the normalized thickness measurements upon irradiation. The copolymer film was effectively cross-linked upon irradiation with 254 nm UV light, and the cross-linking reaction progressed further with increasing irradiation dose and the amount of PMC units in the copolymer. The photochemical formation of the isocyanato groups was evidenced by comparing the IR absorption spectral changes of the exposed and masked copolymer film. The photo-crosslinking reaction of the copolymer was further studied by using a model compound. The results indicated that the cross-linking reaction occurred because of the formation of urea-type chemical bonds, which were produced through the reaction of the photochemically produced isocyanato and amino groups in the copolymer. A negative micropattern was obtained by using the photo-crosslinking reaction.     

Polymerization of coordinated monomers. III. Copolymerization of acrylonitrile–zinc chloride,methacrylonitrile–zinc chloride or methyl methacrylate–zinc chloride complex with styrene

The 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl₂ was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl₂ gave a copolymer containing about 50 mole-% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge-transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge-transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex.     

Hydrolysis of dextrin in the presence of block copolymer of vinyl alcohol and styrenesulfonic acid

A block copolymer of vinyl alcohol and styrenesulfonic acid was prepared by a two-step polymerization and subsequent modification, and its catalytic activity on the hydrolysis of dextrin was investigated. The hydrolysis rate in the presence of the copolymer containing more vinyl alcohol-repeating units was found to follow Michaelis–Menten-type kinetics, whereas that in the presence of a copolymer containing fewer vinyl alcohol units proceeded according to ordinary second-order kinetics. The process of complex formation for the former system was characterized by pronounced decreases in enthalpy and entropy, although the enthalpy and the entropy of activation for the decomposition of the complex to product was comparable to that of a sulfuric acid-catalyzed system. The maximum rate enhancement obtained in the present experiment was approximately fivefold on the basis of the reaction in the presence of sulfuric acid at 65°C. The results were compared with those obtained in the presence of a random copolymer catalyst, previously reported.     

The first example of the copolymerization of cyclic acid anhydrides with oxetane by bulky titanium bisphenolates

The copolymerization of oxetane with glutaric anhydride was found to proceed with bulky titanium bisphenolate ( 1 ) as the initiator. The ¹H NMR spectrum of the produced copolymer shows that the copolymer contains both alternating units and oxytrimethylene units in the polymer main chain. 1 was also effective for the copolymerization of oxetane with other cyclic acid anhydrides, affording the corresponding copolymers. With the titanium bisalkolate complex ( 4 ), a copolymer rich in alternating sequences was obtained.     

Immobilization of glucose oxidase on the films prepared by electrochemical copolymerization of pyrrole and 1-(2-carboxyethyl)pyrrole for glucose sensing

Glucose oxidase (GOx) was immobilized through amide linkages on the surfaces of the conducting polymer films prepared by electrochemical copolymerization of pyrrole (Py) and 1-(2-carboxyethyl)pyrrole (Py-COOH) for the purpose of fabricating GOx-immobilized electrodes for amperometric sensing of glucose. The conductivity of the copolymer film was in the range 10⁻⁸-10⁻³ S/cm and showed a tendency to decrease with increasing content of Py-COOH units in the copolymer. The amount of immobilized GOx increased significantly with increasing content of Py-COOH units in the copolymer film up to 30%, and showed a tendency to level off when the content of Py-COOH units became larger. The activity of immobilized GOx per area of the copolymer film decreased slightly with increasing content of Py-COOH units in the copolymer. Although the GOx-immobilized copolymer films gave the amperometric response to glucose depending on its concentration, the magnitude of the response to a given concentration was found to decrease with increasing content of Py-COOH units in the copolymer. The variation in the amperometric response was attributed to the difference in conductivity of the copolymer film. The appropriate content of Py-COOH units in the copolymer was considered to be 5% or less for the amperometric sensing of glucose with the GOx-immobilized copolymer film.     

Effect of the incorporation of amino groups in a glucose-responsive polymer complex having phenylboronic acid moieties

A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N-vinyl-2-pyrrolidone (NVP), 3-acrylamidophenylboronic acid (AAm-PBA) and N,N-dimethylaminopropylacrylamide (DMAPAA) (poly(NVP-co-PBA-co-DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP-co-PBA-co-DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm-PBA (poly(NVP-co-PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP-co-PBA-DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP-co-PBA-co-DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose-responsive delivery system for insulin.     

Reaction of the acrylic acid and 1-vinylimidazole copolymer with CuCl2 in aqueous solution

The reaction of acrylic acid—1-vinylimidazole copolymer with CuCl₂ in an aqueous medium was investigated by potentiometric titration and UV and ESR spectroscopy. The complex formation involves both the azole units and the carboxy groups. The Cl^– ions are also incorporated in the inner sphere of the complexes, their removal by dialysis resulting in an increase in the coordination capacity of the carboxylate groups.     

Preparation of macroreticular redox resins with hydroquinone and catechol units as pendant groups and their properties

Macroreticular redox resins with hydroquinone and catechol units as pendant groups were prepared by the Friedel-Crafts reaction of macroreticular styrene/divinylbenzene copolymer with 2,5- and 3,4-dimethoxybenzyl chlorides, followed by removal of the methyl groups with hydrobromic acid. The redox capacity of the macroreticular resins was determined by oxidation of hydrazobenzene with resins in oxidized form. Resins with 1,4-benzoquinone units were capable of oxidizing hydrazobenzene, whereas those with 1,2-benzoquinone (catechol quinone) units exhibited no apparent oxidative ability; this seems to be due to a complex formation between azobenzene and the catechol units in the reduced resins. Adsorption of metallic ions onto catechol-containing resins showed a high selectivity for Hg²⁺ ion. The effects of pH, reaction time, and ion concentration on the adsorption were also studied.     

Supramolecular Complex of Poly(styrene)-b-Poly(4-vinylpyridine) and 1-Pyrenebutyric Acid in Thin Film

Summary: Here, we have described a novel supramolecular complex (SMC) between poly(styrene)-b-poly(4-vinylpyridine) (PS-b-P4VP) and 1-pyrenebutyric acid (PBA) and studied of its self assembly in thin film. PBA will make supramolecular complex with the P4VP block due to strong hydrogen bonding between the carboxylic group of 1-pyrenebutyric acid and pyridine ring of P4VP. The formation of supramolecular complex between PS-P4VP and PBA through hydrogen bonding is investigated through FTIR study. The supramolecular complex of PS-b-P4VP and 1-pyrenebutyric acid changed the block copolymer morphology from cylindrical to lamella in thin film due to the increase of the volume fraction of P4VP (PBA). In both cases (parent block copolymer and SMC), the microdomains are oriented normal to the substrate after annealing in a selective solvent. Pure block copolymer shows cylindrical morphology with a periodicity of ∼26 nm, whereas the SMC shows lamellar morphology with a periodicity of ∼ 29 nm. After fabricating the thin film from SMC, 1-pyrenebutyric acid can be easily removed by dissolving the thin film in ethanol to transform the block copolymer thin film into nanotemplate or membrane.     

Selective Interpolymer Complexation between Acrylic Copolymers and Nonionic Polymers

Abstract

Selective interpolymer complexation has been studied between methacrylic acid-methacrylamide copolymer and some complementary polymers such as poly(methacrylamide), poly(vinyl pyrrolidone), and poly(ethylene oxide). The relative order of complexation ability of the various nonionic polymers has been interpreted on the basis of the nature of interactions between different units of polymers. Configurational environment and neighboring group influences seem to affect interpolymer complex formation.     

Polymer Melt Intercalation in Clay Modified by Diblock Copolymers

Summary: The thermodynamic equilibrium in a melt of homopolymer C mixed with clay modified by a diblock copolymer AB is considered in theory. It is assumed that mixing is carried out in two stages. At first, the diblock copolymer penetrates into the interlayers formed by long clay sheets. Then, the clay with adsorbed diblock copolymer chains is added to the homopolymer melt. It is shown that the first process is thermodynamically favorable only if the interlayer width exceeds some threshold value that depends mostly on the difference in the adsorption energy of units A and B. A spontaneous mixing at the second stage is possible only if the enthalpic interactions between homopolymer and copolymer units are not very unfavorable. If so, the formation of an intercalated state is expected for a homopolymer of length comparable to the copolymer length, while for a long homopolymer the anticipated equilibrium state is exfoliation. The spatial distribution of A, B, and C units across the interlayer has been studied for different parameters of the system. The most readily adsorbing units A occupy almost all clay surface. However, the layer of block A is considerably swelled by both B and C units. The mutual distribution of units B and C may vary from almost homogeneous to having rather sharp boundary depending on the value of the Flory‐Huggins parameter χ_BC. The formation of a pure homopolymer layer at the center of the interlayer indicates about a tendency to exfoliate.

Interlayer profiles of the fractions of units A, B, and C, respectively.     

Thermal behaviour of binary and ternary copolymers containing acrylonitrile

Three types of acrylonitrile copolymers (acrylonitrile-styrene-butadiene copolymer (ABS¹), acrylonitrile-styrene random copolymer (SAN²) and acrylonitrile-butadiene random copolymer (BAN³) were studied by thermogravimetry (TG/DTG⁴) and by pyrolysis in a semi-batch process at 450 °C in order to find structure–thermal behaviour relationships. The overlapped thermo-oxidative degradation processes were separated and the corresponding kinetic parameters were calculated. The TG/DTG studies have evidenced that the styrene-acrylonitrile interactions stabilize the nitrile groups reacting by chain scission rather than cyclization and destabilize the styrene units. Also, the cyclization of the acrylonitrile units in ABS is favoured by interactions with the styrene and butadiene units. The pyrolysis behaviour evidenced that the styrene-acrylonitrile interactions in SAN and ABS lead to the formation of 4-phenylbutyronitrile as the most important decomposition compound. ABS shows similar composition of the degradation oil with SAN copolymer therefore in the ABS the styrene-butadiene interactions are less important than those between styrene and acrylonitrile units.     

Thermal Degradation of Trioxane-Dioxqlane Copolymers Obtained with Boron Trifluoride-Acrylonitrile Complex as Initiator

The thermal degradation of certain trioxane-dioxolane copolymers obtained with boron trifluoride-acrylonitrile complex as initiator has been investigated. The thermal stability of samples, discussed in terms of topoenergetic values, was related both to copolymer composition and conversion. The most thermostable copolymers (～5% weight loss at 300°C in air), having 5–8% dioxolane units, had the highest intrinsic viscosity in the series and were isolated at 35–50% conversion. The results obtained were compared with similar data for a commercial tri-oxane-ethylene oxide copolymer containing 95% formal units.     

Photovoltaic properties of bulk heterojunction solar cells incorporating 2-hydroxylethyl- and fullerene-functionalized conjugated polymers

We have synthesized a series of maleimide–thiophene copolymers presenting pendent 2-hydroxylethyl and fullerene units for use as photo-energy conversion materials in polymer solar cells (PSCs), which we fabricated from blends of these maleimide–thiophene copolymers and the fullerene derivative [6, 6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). A too-homogenous distribution of the 2-hydroxylethyl-functionalized copolymer and PCBM inhibited charge separation and transport in the photoactive layer. Introducing fullerenes as pendent units of the copolymer promoted the formation of phase-separated interpenetrating networks with sizable PCBM domains in the photoactive layer, favorable for transporting charges to the electrodes. The photovoltaic performance and operational stability of PSCs based on the fullerene-functionalized copolymer/PCBM blends were superior to those based on the hydroxyethyl-functionalized copolymer/PCBM blends.     

Synthesis and characterization of copolymers of β-cyclodextrin derivatives

Cyclodextrins (CDs) are cyclic oligosaccharides made up of d-glucose units connected by 1,4-glucosidic linkages. β-CD is a cyclical starch derivative containing seven glucopyranose units. β-CD derivatives have characteristic property of larger surface area, robust mechanical strength, high surface to volume ratio, electrical and optical properties for analyte determination, good dispersion, easy removal of the template, surface modification, functionalization and handling capacity. In this work, an attempt is made to prepare succinyl-β-CD-acrylamide (S-β-CD-AA) copolymer and β-CD-malic anhydride (β-CD-MAH) copolymer. For the synthesis of S-β-CD-AA, S-β-CD derivative is prepared and further, acrylamide (AA) along with cross-linker undergoes free radical copolymerization for the formation of gel like product. The degree of succinylation (DS) of β-CD derivative is estimated. S-β-CD-AA copolymer showed potential swelling, and deswelling characteristic. Another copolymer is prepared from β-CD malic anhydride derivative. Further, the derivative is treated with cellulose and ethylene diamine tetra acetate (EDTA) to form β-CD-MAH copolymer. The two derivatives are characterized by several techniques. Thermal stability of these copolymers is estimated with the help of thermogravimetric analysis. The basic characterization of the presence of functional groups is done using UV–visible spectroscopy, and infrared spectroscopy. The elemental analysis helped to estimate C, H, N, S in the synthesized compounds. The surface morphology characterization is done with the help of scanning electron microscopy. X-ray diffraction analysis helped in determination of crystal structure of β-CD-MAH. β-CD derivatives prepared may be potential candidate to prepare inclusion complex, in drug delivery, drug loading and several similar applications.     

Alternating Sequence Control for Carboxylic Acid and Hydroxy Pendant Groups by Controlled Radical Cyclopolymerization of a Divinyl Monomer Carrying a Cleavable Spacer

By utilizing features of the hemiacetal ester (HAE) bond: easy formation from vinyl ether and carboxylic acid and easy cleavage into different functional groups (‐COOH and ‐OH), we achieved control of the alternating sequence of two functional pendant groups of a vinyl copolymer. Methacrylate‐ and acrylate‐based vinyl groups were connected through HAE bonds to prepare a cleavable divinyl monomer, which was cyclo‐polymerized under optimized conditions in a ruthenium‐catalyzed living radical polymerization. Subsequent cleavage of the HAE bonds in the resultant cyclo‐pendant led to a copolymer consisting of alternating methacrylic acid and 2‐hydroxyethyl acrylate units as analyzed by ¹³C NMR spectroscopy. The alternating sequence of ‐COOH and ‐OH pendants specifically provided a lower critical solution temperature (LCST) in an ether solvent, which was not observed with the random copolymer of same composition ratio.     

Increase in the content of maleic anhydride units in a copolymer with methyl methacrylate in the presence of 1,3,5-trithiane

The use of 1,3,5-trithiane as agent controlling copolymerization of maleic anhydride with methyl methacrylate allows preparation of the copolymer with increased content of anhydride units because of the radical complex mechanism of the process under these conditions.     

Compatibilization of copolymers in solution through interchain hydrogen bonding

Low concentrations of polar units interacting through hydrogen bonds were introduced in polystyrene and polyvinylacetate chains by free radical copolymerization. Phase diagrams of copolymer mixtures in tetrahydrofuran were investigated. The influences on cloud-point isotherms of polar comonomer nature and concentration, and of copolymer molecular weight were studied. Viscometry appears to be reliable for evaluating the interactions betwen the different copolymers synthesized.     

Molecular and supramolecular structures of complexes formed by polyelectrolyte‐surfactant interactions: effects of charge density and compositions

The process of complex formation and the structure of the complexes were studied for the surfactant binding of the N‐alkylpyridinium chlorides (C_nPyCl, n = 12, 16) to the sodium salt of poly(styrenesulfonate) (NaPS) and its copolymer with styrene. Both the NaPS and the amphiphilic copolymer form non‐stoichiometric complexes with an excess of the cationic surfactants. The NaPS‐complex with pronounced short‐range (d₁) and long‐range (d₂) orderings is insoluble, and the amphiphilic copolymer‐complex is water‐soluble when bound with extra charges. The mechanism of the complex formation was discussed in terms of the charge density and chemical composition of the polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 635–644, 1999