Journal of Polymer Science Part A: Polymer Chemistry

This highlight aims to reflect the critical role the noncovalent forces play in controlling macromolecular structures, which hold immense untapped potential for applications defying conventions, and briefly touches on the concept of homochirality in nature based on chiral and weak noncovalent interactions in synthetic nonpolar polysilanes. It also sheds some light on the discovery and characterization of Si/F-C interactions in fluoroalkylated rod-like polysilanes for which we found application in the field of chemosensing of fluoride ions and nitroaromatic compounds with a great degree of sensitivity and selectivity. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

The polymer monoliths based on glycerin 1,3-dimethacrylate (GDMA) were investigated applying photoinitiated in situ polymerization for HPLC of small solute molecules. The ultra high molecular weight monodisperse polystyrene (M_w = 8,420,000, 1% w/v) solution in chlorobenzene was utilized uniquely as a porogen. The poly-GDMA capillary of 100 μm i.d. was fabricated by 365-nm UV irradiation at 20 °C for 24 h. The prepared capillary revealed a bicontinuous network-like structure (as shown in SEM), presumably frozen by photoinitiated in situ polymerization via viscoelastic phase separation induced by the said porogen. GDMA/PS solution in chlorobenzene = 33/67, v/v.

Triaryl diamine-based low-molar-mass compounds and polymer were synthesized and studied as potential hole-transporting materials. Their thermal, optical and photoelectrical properties were studied. The synthesized compounds are capable of glass formation. Their glass transition temperatures range from 43 to 119 °C. The ionization potentials are in the range 5.31–5.40 eV. Time-of-flight hole mobilities up to 10⁻³ cm²/Vs were observed at high electric fields.

PTMA–lysozyme and PIMA–lysozyme complexes formed when mixing negatively charged PTMA or PIMA with positively charged lysozyme. Hydrophobic interaction in PTMA–lysozyme complex causes lysozyme to lose its tertiary structure and activity completely. NaCl is more effective to dissociate PIMA–lysozyme complex by screening the electrostatic interaction, while GdHCl is more effective to dissociate PTMA–lysozyme complex by forming GdHCl–PTMA precipitates through extra hydrophobic interaction. The released lysozyme can fully regenerate its native structure and activity. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

The synthesis and characterization of hydrogen-bonded star-shaped complexes consisting of stilbazolyloxy, azopyridyl, and Schiff base-substituted cyclotriphosphazenes and monoalkyloxy, bis(dodecyloxy), and tris(dodecyloxy)benzoic acids are reported. The thermal behaviors of complexes are studied by the means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. Cyclotriphosphazenes with monoalkyloxybenzoic acids show a homeotropic smectic A mesophase. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Using mild condensation polymerization conditions nearly perfectly alternating atactic and isotactic PLGA copolymers were synthesized. Sequence- and stereocontrol were confirmed by high resolution ¹H and ¹³C NMR spectroscopy. The ¹H NMR resonances associated with the diastereotopic methylene groups were found to be the most sensitive to tacticity; tetrad level resolution of the backbone stereochemical relationships was observed. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Thermally enhanced photoinduced in-plane molecular reorientation in new photo-cross-linkable polymer liquid crystalline films is explored using linearly polarized ultraviolet light exposure and subsequent annealing. The influence of the alkylene spacer length between the photo-cross-linkable group and the biphenyl mesogenic moiety is investigated. The straight-line characteristics of the photoreactive mesogenic side group and the 4-methoxycinnamoyl group play important roles in the high photoreactivity and the large thermally enhanced molecular reorientation, where the in-plane order and the birefringence of the reoriented film are 0.61 and 0.18 are obtained. Cooperative molecular reorientation of dichroic dyes doped in PPLC films is also achieved to fabricate a linear polarizer.

The self-assembly in thin film of a metallo-supramolecular block copolymer is studied. We show that the behavior of the PS-[Ru]-PEO copolymer, where -[Ru]- is a bis-2,2′:6′,2″-terpyridine-ruthenium(II) complex, is strongly affected by the presence of this charged complex. PEO cylinders oriented normal to the surface are obtained over a wide range of thicknesses independently of the experimental conditions. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Half titanocenes (CpCH₂CH₂O)TiCl₂ (1), (CpCH₂CH₂OCH₃)TiCl₃ (2), and CpTiCl₃ (3), activated by methylaluminoxane (MAO) were able to give copolymerization of ethylene with internal olefins (i.e. cyclopentene, E and Z, –2-butene). ¹³C NMR analysis of obtained copolymers showed that the catalytic systems have low regiospecificity. In fact, in ethylene-–cyclopentene copolymers cyclic monomer insert with both 1,2 and 1,3-enchainment. In ethylene-2-butene copolymers 2-3, 1-3, and 1-2 insertion of 2-butene were detected. Differential scanning calorimetry and X-ray powder diffraction analysis proved that the copolymers are crystalline.

The controlled regioselective cationic polymerization of cyclopentadiene can be achieved using 1-(4-methoxyphenyl)ethanol (1)/B(C₆F₅)₃ initiating system in the presence of fairly large amount of water and mild experimental conditions. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Homopolymers and copolymers of these fluoroalkyl methacrylates with methyl methacrylate (MMA) were prepared and characterized. The glass transition temperatures (T_g) of the copolymers were found to deviate positively from the Gordon-Taylor equation (except 1/MMA system). The refractive indices of the copolymers were lower than that of PMMA and showed a linear relationship with monomer composition in the copolymers. The copolymer, prepared with an equal molar ratio of 2 and MMA, has an alternating uniform monomer composition and less light scattering, and therefore may have useful properties with applications in optical devices.

Polysulfone-g-poly(N-isopropylacrylamide) (PSf-g-PNIPAAm) graft copolymers were prepared from atom transfer radical polymerization (ATRP) of NIPAAm using chloromethylated PSf as a macro-initiator. The chain lengths of PNIPAAm of the graft copolymers were controllable with polymerization reaction time. The chemical structures of the graft copolymers were characterized with FTIR, NMR, and elemental analysis and their amphiphilic characteristics were examined and discussed. The PSf-g-PNIPAAm graft copolymers and the nanoparticles made from the graft copolymers exhibited repeatable temperature-responsive properties in heating–cooling cycles. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

In the presence of an anionic catalyst such as sodium caprolactam (NaCL), ε-caprolactam (CL) can be polymerized from an isocyanate bearing polystyrene (PS) to form a graft copolymer of PS and PA6 denoted as PS-g-PA6. This paper shows that each isocyanate moiety leads to the formation of a PA6 graft and that the resulting product is composed of a pure PS-g-PA6, homo-PA6 and CL residue.

Acidic bismuth salts catalyze cationic polymerizations of 2-alkyloxazolines, whereby linear chains having one cationic chain end are formed which reacts quantitatively with strong nucleophiles.

Multiblock copolymers containing linear and hyperbranched blocks of poly(ether sulfone) were prepared by one-pot, two-step method. The resulting product contains regions of dense functionality from the hyperbranched blocks separated by oligomeric linear chains. The AB to AB₂ composition of the polymer is identical to that of the initial monomer ratio indicating that this method offers precise control over the final polymer composition. The physical properties of the product have intermediate thermal stability and T_g to those of the individual homopolymers. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

This paper article presents a simple method for synthesis and hydrolysis of a new phosphonated methacrylate: dimethyl(methacryloyloxy)methyl phosphonate (MAPC₁). Copolymerization of this monomer with MMA led to a new additive of PVDF that enhances both adhesion and anti-corrosion properties of a metal steel plate.

The effect of initiator on the resulting monomer distribution for the cationic ring-opening copolymerization of 2-ethyl-2-oxazoline and 2-phenyl-2-oxazoline was studied. First, the polymerization kinetics and the presence of cationic species during the homopolymerizations were studied utilizing four different initiators with the same benzyl initiating group but different leaving groups. The basicity of the leaving group affects the ratio of covalent and cationic propagating species and, thus, the polymerization rate. To determine the monomer distribution in the copolymers, a new approach was used to calculate the reactivity ratios for the copolymerizations, which allow more accurate determination of the copolymerization parameters compared to conventional methods. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Functionalized poly(phenylene-alt-bithiophene)s are prepared and their chiroptical properties are studied. Addition of chiral amines to achiral, carboxylic acid-functionalized polymers results in chiral aggregation.

Thermosensitive anionic block copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) and N-isopropylacrylamide (NIPAAM) with different block lengths were prepared by atom transfer radical polymerization (ATRP). Blocks lengths ranging from 36 to 98 repeating units were obtained. The association properties in aqueous solutions at different NaCl ionic strengths were studied as a function of temperature and polymer concentration. The block copolymers with a higher pNIPAAM/pAMPS ratio formed spherical core-shell type micelles. At high ionic strength, lower pNIPAAM/pAMPS ratio gave core-shell type micelles. Larger particles were observed at low ionic strength, which could be due to the formation of vesicles or compound micelles/micellar clusters.

New methods for the successful preparation of stereoregular diblock copolymers via post-polymerization of end-functionalized stereoregular prepolymer were reported in this article. The resulting stereoregular diblock copolymer possesses precise chemical architecture to self-organize into consistent nanostructures as evidenced by transmission electron microscopy and small angle X-ray scattering.

MWCNTs were first grafted with an interlayer of poly (acryloyl chloride) (PACl) to enhance the surface of MWCNTs. The remaining acryloyl chloride groups were allowed to be esterified with a proper amount of ethylene glycol (EG). In situ covalent encapsulation of MWCNTs by polyurethane (PU) was realized via the reaction between isocyanate groups of MDI and hydroxyl groups of BDO and those remaining on EG in a state of suspension. Encapsulated MWCNTs thus obtained were well pre-dispersed, providing an effective interfacial adhesion with PU matrix. Consequently, an improvement in mechanical properties of nanocomposites was achieved.

Two novel electroluminescent (EL) polymers with same backbone poly(dinaphtho[1,2-a:1′,2′-g]-s-indacene) and different side chains have been synthesized and characterized. They have extended conjugation along the direction perpendicular to the backbone by introducing naphthalene moieties, which result in stable film morphology. The emission of both polymers in film state is strongly dependent on the substituents. The new broad-bandgap polymer with high EL efficiency and spectral stability can be used not only as an efficient EL material, but also as a host material for constructing polymers to emit low- energy light or white light. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Olefin group-carrying styrene, 1-but-3-enyl-4-vinylbenznene (BVB), was polymerized via atom transfer radical polymerization (ATRP) initiated from C-methylcalix[4]resorcinarene-based multifunctional initiator (CRA-bib) at low conversion to produce star polymer (poly(BVB)) with narrow molecular weight distribution. The copolymerization of styrene (St) with poly(BVB) as a macroinitiator afforded star block copolymer (poly(BVB-b-St)). The BVB layer of poly(BVB-b-St), located between the St shell and the CRA core, was cross-linked by olefin metathesis reaction of olefin groups of the BVB moieties. The removal of the CRA core of the cross-linked poly(BVB-b-St) by hydrolysis using KOH as a base gave polymeric hollow sphere (poly(cored crossBVB-b-St)) with good solubility in organic solvents. The nanocapsule structure of poly(cored crossBVB-b-St) with hollow spheres was observed by transmission electron microscopy (TEM).

A series of novel “jellyfish-like” graft copolymers with chitooligosaccharide as shorter backbone and poly(ε-caprolactone) as longer branches were synthesized. The obtained chitooligosaccharide-graft-poly(ε-caprolactone) polymers possess amphiphilic structure with hydrophilic chitooligosaccharide backbone and hydrophobic polycaprolactone branches. Because of this unique “jellyfish-like” structure, these graft copolymers could self-assemble to form various morphologies of aggregates in a mixture solution of water and tetrahydrofuran, including interconnected vesicles, flower-like aggregates, onion-like vesicle, and tubules. It is found that the hydrogen-bonding formed by the hydroxyl and amino groups remained on the chitooligosaccharide backbone played an important role during the aggregation of these graft copolymers, and their morphologies were changed with the varying the length of poly (ε-caprolactone) branches, the concentration of the graft copolymer, and the self-assembly process. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Brominated aromatic acrylates were found to initiate the UV-induced polymerization of acrylic formulations without a conventional photoinitiator even if they are added only in low concentration. Investigations by real-time FTIR spectroscopy show that fast photopolymerization is achieved even if irradiation is carried out at λ > 300 nm. In contrast, the corresponding unbrominated homologues are not effective as initiators. Quantum yields for the formation of bromine radicals were found to be in the range of up to 0.3. Quantum chemical modeling was carried out to establish a mechanism for the release of bromine radicals. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

The Single-Electron Transfer Living Radical Polymerization (SET-LRP) of methyl acrylate initiated with methyl-2-chloropropionate (MCP) and chloroform (CHCl₃) catalyzed by Cu(0)/Me₆-TREN/CuCl₂ in DMSO at 25 °C is reported. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl₃ initiating behavior under SET-LRP conditions. These results demonstrate that SET-LRP has a small dependence of on the nature of halogen responsible of the propagation step and therefore provides access to economic synthesis of macromolecules via optimum initiator selection. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

In this work, we report a new peptide RATEA16 nanofiber hydrogel as a drug delivery system for protein, and the protein-nanofiber assemblies are formed based on hydrophobic and electrostatic interactions. The loading/release process is reversible by changing media pH, and the protein released from the hydrogel returned its native structure. Therefore, it offers new prospects for preparing peptide hydrogel for special biomedical applications. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]