Investigation of the Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid‐Styrene Copolymer, 1

Summary: The hydrogen bonding‐interpolymer association of hydroxypropyl cellulose (HPC) with maleic acid‐styrene (MAc‐S) copolymer has been investigated in dilute aqueous solution by viscometry, turbidimetry and potentiometry. At a mixing ratio between MAc‐S and HPC of 10:90, the solution exhibits a phase separation upon heating, while for other mixing ratio no phase separation could be detected. The stability of the interpolymer complex (IPC) increases as the temperature rises. The stoichiometry of the IPC, in mole units, was estimated as being MAc‐S:HPC = 5:2. The thermodynamic functions (enthalpy and entropy) of the complexation process have been determined.

Dependence of IPC concentration in H₂O/MAc‐S/HPC system on the mole fraction of MAc‐S in polymer mixture at different temperatures.     

Grafting of Chitosan with Styrene and Maleic Anhydride via Nitroxide‐Mediated Radical Polymerization in Supercritical Carbon Dioxide

A novel synthesis route is used to produce chitosan‐graft‐poly(styrene‐maleic anhydride)‐OH‐TEMPO (CTS‐g‐PSMA‐T). A three‐step reaction scheme is proposed: 1) bromine 4‐OH‐TEMPO oxoammonium salt is synthesized. 2) Hydroxyl‐targeted groups in the CTS molecule are reacted with the synthesized salt in aqueous acid solution. A functionalization of 18.9% is achieved. 3) Graft copolymerization of styrene and maleic anhydride is done via NMRP by a unimolecular initiation system. The reaction is run in a dispersion in supercritical carbon dioxide (scCO₂) in the presence of camphorsulfonic acid (CSA) to avoid autopolymerization. A modified CTS with a graft content of 68% in weight is obtained.

     

Comparison of Styrene with Methyl Methacrylate Copolymers on the Adhesive Performance and Peeling Master Curves of Acrylate Pressure Sensitive Adhesives

Summary: Styrene (S) and methyl methacrylate (MMA) copolymers were prepared with acrylates, such as butyl acrylate, 2‐ethylhexyl acrylate and acrylic acid, for application as pressure sensitive adhesives (PSA). The copolymer compositions were designed to provide constant glass transition temperature. The PSA were tested using peel adhesion resistance, static shear resistance, loop tack and DMA. Time‐temperature‐superposition (TTS) was used to construct peel resistance master curves to compare copolymers containing S and MMA, and obtain a structural interpretation of the PSA performance. The TTS master curves were combined for related copolymer series to obtain composition super master curves. The super master curve construction demonstrated the comonomer composition dependence of the PSA performance and distinguished copolymers containing S from those containing MMA. Composition related performance was exhibited by static shear and loop tack, the latter in relation to the concentration shift factors. DMA results confirmed the adhesive performance interpretations. Composition super master curves suggested differences in the relative mobility of S and MMA copolymers. Chain branching and entanglements were more significant with MMA than with S copolymers. DMA and static shear resistance confirmed the peel resistance results. S copolymers decreased the loop tack consistent with their higher molecular weight and lower polydispersity, with fewer low molecular weight fractions contributing to the tack. MMA copolymers dissipated more energy under high stress than S copolymers.

Example peel master curve for formulation AA4M91‐2 (reference temperature: T₀ = 298 K).     

High Ionic Strength Promotes the Formation of Spherical Copolymer Particles

A comprehensive experimental study of thermally initiated styrene‐styrene sulfonate emulsion copolymerization in the presence of 15 different low‐molecular‐weight electrolytes clarifies the enormous influence of both the concentration and nature of the added salt on the outcome of the polymerization. The ionic strength (IS) has a direct influence on the styrene sulfonate content in the final copolymer and determines whether the physical state of the final reaction product is a solution or dispersion. Stable latexes have been obtained for IS as high as 18 M . Electron microscopy images show irregularly shaped clusters at low and spherical particles at high IS. The properties of the copolymer molecules and dispersion can be additionally modified by the chemical properties of the counter‐ and coions introduced with the salt.

     

Interpolymer Complexes between Hydroxypropylcellulose and Copolymers of Maleic Acid: A Comparative Study

Summary: The formation of interpolymer complexes (IPCs) between hydroxypropylcellulose (HPC) and copolymers of maleic acid with vinyl acetate (MAc‐VA), acrylic acid (MAc‐AA) and styrene (MAc‐S) in aqueous solution has been investigated by turbidimetry, viscometry and fluorescence measurements. The viscosity data indicated a compact structure for the IPCs between HPC and maleic acid copolymers. Besides H‐bonding, strong hydrophobic forces materialize between HPC and MAc‐S, strengthening this IPC. The strength of the interpolymer interactions was estimated to increase in the order: HPC:MAc‐VA < HPC:MAc‐AA < HPC:MAc‐S. The IPCs of HPC with MAc‐VA or MAc‐AA were water‐soluble at pH values higher than 3, while the IPC between HPC and MAc‐S was water‐soluble at pH values above 4.5.

Cloud point temperature of different interpolymer complexes as a function of copolymer concentration.     

π‐Conjugated Polymers Consisting of Isothianaphthene and Dialkoxy‐p‐phenylene Units: Synthesis,Self‐Assembly,and Chemical and Physical Properties

A series of π‐conjugated alternating copolymers consisting of Th‐ITN‐Th and p‐C₆H₂(OR)₂ units were synthesized. XRD indicated that the copolymers assume an interdigitation packing mode, and UV‐Vis spectra revealed a strong tendency for self‐assembly. Upon molecular assembly of the copolymer, the UV‐Vis absorption shifted by about 100 nm to a longer wavelength from that of the single molecule. The copolymers underwent electrochemical oxidation (or p‐doping) and reduction (or n‐doping) at 0.2 and ?2.0 V versus Ag⁺/Ag, respectively. A p‐doped copolymer film showed an electrical conductivity of 182 S · cm^?1, and the temperature dependence of electrical conductivity was measured. The copolymer showed piezochromism and served as a p‐channel material for a field‐effect transistor.

     

Crystallization and Ring‐Banded Spherulite Morphology of Poly(ethylene oxide)‐block‐Poly(ε‐caprolactone) Diblock Copolymer

Summary: The crystallization behavior of crystalline‐crystalline diblock copolymer containing poly(ethylene oxide) (PEO) and poly(ε‐caprolactone) (PCL), in which the weight fraction of PCL is 0.815, has been studied via differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized optical microscopy (POM). DSC and WAXD indicated that both PEO and PCL blocks crystallize in the block copolymer. POM revealed a ring‐banded spherulite morphology for the PEO‐b‐PCL diblock copolymer.

DSC heating curve for the PEO‐b‐PCL block copolymer.     

Unique morphology of amorphous polystyrene synthesised by nickel bis(acetyl acetonate)/methylaluminoxane

Polystyrene synthesised at room temperature by nickel bis(acetyl acetonate)/methylaluminoxane is globally atactic and amorphous in solid state. Unexpectedly, the amorphous polystyrene displays, in addition to normal amorphous scattering, a Bragg X‐ray diffraction at 2θ = 14°. This sharp reflection has been related to the presence of individual isotactic polystyrene sequences, as shown by ¹³C NMR. The isotactic sequences are long enough so that they are likely to form 3₁ helices, but not necessarily significantly laterally ordered and crystalline in solid state.

WAXD diagrams of (1) polystyrene synthesised by Ni(acac)₂/MAO; (2) poly(styrene‐co‐norbornene), styrene content 28.4 mol‐%; (3) poly(styrene‐co‐norbornene), styrene content 9.5 mol‐%; (4) polynorbornene.     

Electroactive Copolymers with Oligoanilines in the Main Chain via Oxidative Coupling Polymerization

Summary: By oxidative coupling polymerization of the macromonomer of oligoaniline and p‐phenylenediamine, we have prepared an electroactive copolymer, exhibiting an exciting molecular structure, and interesting spectroscopic and electrochemical properties. The polymerization characteristics and structure of the copolymer were systematically studied by gel permeation chromatography (GPC), Fourier‐transform infrared (FTIR) spectroscopy, ¹H NMR spectroscopy and X‐ray powder diffraction (XRD). UV‐vis spectra were used to monitor the chemical oxidation process of the reduced copolymer. The electrochemical activity of the copolymer was tested in 1.0 M H₂SO₄ aqueous solution. Three redox peaks were shown, which is different to that for polyaniline. The thermal properties of the copolymer were also evaluated, by thermogravimetric analysis (TGA); the electrical conductivity is about 5.53 × 10^?5 Scm^?1 at room temperature, upon a preliminarily, proton‐doped experiment.

Synthesis of the copolymer.     

Proton‐Conducting Properties of Acid‐Doped Poly(glycidyl methacrylate)‐1,2,4‐Triazole Systems

1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, ¹³C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower T_g and higher proton conductivities. PGMA‐Tri 4 H₃PO₄ showed a maximum water‐free proton conductivity of approximately 10^?2 S · cm^?1 while that of PGMA‐ATri 2 H₃PO₄ was 10^?3 S · cm^?1. The structure and dynamics of the polymers were explored by ¹H MAS and ¹³C CP‐MAS solid‐state NMR.

     

Can the First Addition of Alkyl Radicals Play a Role in the Fate of NMP?

Values of k_d for the C? ON bond homolysis were measured for alkoxyamines based on imidazoline and imidazole nitroxides. They were analyzed in terms of polar/stabilization, steric, and entropic effects. k_d decreased with increasing electron‐withdrawing capacities of the groups attached to the nitroxide, but increasing with both the bulkiness of the group attached to the nitroxide and the presence of substituents on the ring. With three alkoxyamines, it was shown that the fate of the NMP of styrene depended on the type of initiating alkyl radical: successful for initiating 1‐phenylethyl radicals and unsuccessful for initiating p‐nitrophenyloxycarbonyl‐2‐prop‐2‐yl radicals.

     

Gas‐Phase Assisted Surface Polymerization of Vinyl Monomers with Fe‐Based Initiating Systems

Summary: Gas‐phase assisted surface polymerization (GASP) of methyl methacrylate (MMA) and styrene (St) was investigated with Fe‐based radical initiating systems, FeCl₂/2,2′‐bipyridine (Bpy)/methyl α‐bromophenylacetate (MBPA), etc. GASP with these initiating systems proceeded to produce corresponding polymers on substrate surfaces. The resulting PMMA had very high PDI values, suggesting an uncontrolled reaction. In an attempt to control the GASP, polymerization with a simple initiating system, Fe(0)/MBPA, was examined on Fe(0)‐metal surfaces, resulting in significant polymerization activity to produce high‐molecular‐weight PMMA. The results of time‐course tests on GASP of MMA and St suggested that a change had taken place to produce physically controlled propagation sites on the Fe(0) powder surfaces.

GASP schemes with a simple initiating system Fe(0)/MBPA.     

Synthesis and Characterization of Alternating and Random Copolymer Brushes

Alternating free‐radical copolymerization of vinylbenzyl‐ and methacryloyl‐terminated macromonomers in the presence of Lewis acid was applied to the synthesis of prototype copolymer brushes composed of polystyrene/poly(ethylene oxide) (PS/PEO) alternating structure. Random copolymer brushes were also prepared by radical copolymerization of both macromonomers in the absence of Lewis acid. It was found from dilute solution properties that both copolymer brushes composed of short aspect ratio formed an ellipsoid‐like single molecule in solution. To discuss the intramolecular phase separation of PS/PEO brushes in solution, we determined the radius of gyration (R_g) and cross‐sectional radius of gyration (R_g,c) of copolymer brushes by small‐angle X‐ray scattering (SAXS) using Guinier's plots in DMF and styrene. We used styrene as a solvent to cancel each other out with the electron density of PS side chains. We made also clear the effect of branching topology on polymer crystallinity to be examined by comparing the copolymer brushes with corresponding linear PEO or PEO‐block‐PS block copolymer.

     

Controlled synthesis of anthracene‐labeled ω‐amine polystyrene to be used as a probe for interfacial reaction with mutually reactive PMMA

Anthracene‐labeled polystyrene (PS) end‐capped by a primary amine has been synthesized by atom transfer radical copolymerization of styrene with 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (m‐TMI). The m‐TMI co‐monomer (5.7 mol‐%) does not perturb the control of the radical polymerization of styrene. The pendant isocyanate groups of the copolymer chains of low polydispersity (M _w/M _n = 1.25) and controlled molecular weight (up to 35 000) have been derivatized into anthracene by a reaction with 9‐methyl(aminomethyl)anthracene. The anthracene‐labeled PS (ca. 2 mol‐% label) has been conveniently analyzed by size‐exclusion chromatography with a UV detector (SEC‐UV). Moreover, the ω‐bromide end‐group of the copolymer chains has been derivatized into a primary amine, making the labeled PS chains reactive towards non‐miscible poly(methyl methacrylate) (PMMA) chains end‐capped by an anhydride. The interfacial coupling of the mutually reactive PS and PMMA chains has been studied under static conditions (i.e., at the interface between thin PS and PMMA films) and successfully analyzed by SEC‐UV.

SEC‐UV traces for anth‐PS‐NH₂ (80 μg · ml⁻¹; sample A5; Table 1 ), and PMMA‐anh (80 μg · ml⁻¹; sample B1; Table 1 ).     

The Formation of a Stable,Helical Conformation in Poly(N‐propargylamides) through Synergic Effects among their Pendent Groups

Copolymerization reactions of two N‐propargylamides [ 1 : HC?CCH₂NHCO(CH₂)₅CH₃, 2 : (HC?CCH₂NHCOC(CH₃)₃] were carried out with different monomer feed ratios. Compared with the two corresponding homopolymers, the series of resulting copolymers poly( 1 ‐co‐ 2 ) had a higher helix content. They also performed very differently in conformational transitions, either from random coil to helix or from helix to random coil, mainly depending on the composition of the copolymers. Synergic effects among the pendent groups played a significant role in the copolymer main chains adopting stable helices.

     

Poly(arylene ether)s with Pendant Perfluoroalkyl Sulfonic Acid Groups as Proton‐Exchange Membrane Materials

New membranes were prepared and evaluated as polymer electrolytes for PEMFCs. Polymers with PSU in the main chain and –C(O)(CF₂)₃SO₃H in the side chain (PSU‐PSA) were synthesized by substitution of PSU‐Li and SFBF, followed by treatment with aqueous potassium hydroxide then sulfuric acid. The proton conductivity of PSU‐PSA with an ion exchange capacity (IEC) of 1.12 mmol · g^?1 was 0.091 S · cm^?1 at 80 °C under 100% relative humidity. A hydrogen/air PEMFC test of PSU‐PSA with an IEC value of 1.12 mmol · g^?1 produced a maximum power output of 0.265 W · cm^?2. A DMA measurement revealed that PSU‐PSA had an α‐relaxation temperature around 196 °C which is higher than the value reported for Nafion.

     

Proton‐Conducting Zirconium Pyrophosphate/Poly(2,5‐benzimidazole) Composite Membranes Prepared by a PPA Direct Casting Method

Zirconium pyrophosphate (ZPP)/poly(2,5‐benzimidazole) composites were prepared by polymerization of 3,4‐diaminobenzoic acid with zirconium hydrogen phosphate in polyphosphoric acid. The composite membranes for polymer electrolyte membranes were prepared by casting the polymerization solutions directly onto stainless steel plates. Membranes doped in 60 wt.‐% phosphoric acid solution had high proton conductivity values of more than 0.12 S · cm^?1 (at 180 °C and 1% RH). Physical properties of the doped membranes, including the mechanical strength and dimensional stability, improved as ZPP content in the composites increased to 10–20 wt.‐%.

     

Melt Properties of Poly(styrene‐co‐acrylonitrile) and Poly(butylene terephthalate) and their Interfacial Tension

Pressure‐volume‐temperature and surface tension behaviour were studied for random copolymers of styrene and acrylonitrile (SAN) and for poly(butylene terephthalate) (PBT). Results served to determine reduction parameters for the equation‐of‐states by Flory‐Orwoll‐Vrij and by Simha‐Somcynsky as well. Surface tension as a function of copolymer composition displays negative deviation from additivity. It indicates surface excess of styrene units. Similar behaviour with respect to copolymer composition was found for variation of interfacial tension between SAN and PBT. Thickness of surface region is around 1 nm and does not change with copolymer composition whereas extension of interfacial region between PBT and SAN copolymers varies strongly with copolymer composition between around 2 and 60 nm.

     

Polyaniline with Two Types of Functional Groups: Preparation and Characteristics

Summary: Polyaniline with two types of functional groups (sulfonated poly(aniline‐co‐o‐aminophenol), s‐copolymer) has been prepared by the electrochemical copolymerization of aniline and o‐aminophenol in sulfuric acid solution followed by sulfonation of the copolymer in the concentrated sulfuric acid. There are ? SO₃H groups and ? OH groups in the s‐copolymer. The presence of ? SO₃H groups on the polymer chain enables the s‐copolymer to possess intrinsic protonic doping ability. The ? OH group on the polymer chain can be oxidized and reduced reversibly. The shape of the cyclic voltammogram of the s‐copolymer is very similar to that of polyaniline in 0.2 M H₂SO₄ solution, in the potential range ?0.20 to 0.80 V (vs. SCE). The results from cyclic voltammograms indicate only 22.8 and 31.6% decay of the electrochemical activity that was observed when the s‐copolymer electrode was transferred from the solution of pH 5.0 to the solutions of pH 10.0 and 11.0, respectively. Especially, there are still two pairs of redox peaks on the cyclic voltammogram of the s‐copolymer in 0.3 M Na₂SO₄ solution of pH 11.0 at the scan rate of 6 mV s^?1. In this case, its usable potential range is 0.0–0.60 V. The s‐copolymer has a conductivity of 0.85 S cm^?1, which is slightly dependent on pH when equilibrated with water. The spectra of FTIR, XPS, and ESR of the s‐copolymer are represented here.

The cyclic voltammograms of (1) poly(aniline‐co‐o‐aminophenol) and (2) s‐copolymer in H₂SO₄ solution.     

Ionic‐Strength‐ and pH‐Responsive Poly[acrylamide‐co‐(maleic acid)] Hydrogel Nanofibers

A novel acrylamide/maleic acid copolymer [P(AM‐MA)] hydrogel nanofibrous membrane with a fiber diameter of ca. 120 nm is prepared by electrospinning an aqueous P(AM‐MA) solution with diethylene glycol as crosslinker, followed by a heat‐induced esterification crosslinking reaction at 145 °C. This hydrogel nanofiber can maintain a fiber form, but becomes distorted and merges to form many physical crosslinking points after immersion in water. The P(AM‐MA) hydrogel nanofibers are sensitive to external stimuli ionic strength and pH. Their water‐swelling ratio decreases with increasing solution ionic strength, and it shows a characteristic two‐step increase at pH = 2.5 and 8.5 in response to the increase of solution pH. The maximum water‐swelling ratios of the P(AM‐MA) hydrogel nanofibers are 18.1 and 22.5 g · g^?1 in a solution of 0.05 mol · dm^?3 ionic strength and in an aqueous solution of pH 11, respectively.