Reactive and Functional Polymers (v.76, #C)

Here, we present a novel and facile method for constructing “snowflake-like” assemblies that respond to external stimuli, similar to snowflakes in nature, via the self-organization of ferrocene-modified chitooligosaccharide (FcCOS) in an acid aqueous solution. Interestingly, the snowflakes were sensitive to pH and redox stimuli. They not only formed irregular network-like aggregates when the pH was adjusted to 7.0, they also gradually transformed into loose snowflakes with holes after exposure to air for 5 d and totally collapsed after treatment with hydrogen peroxide. Due to their interesting responses to pH and oxidation, these assemblies are a very interesting and promising system for biomaterial applications.
Keywords: Biodegradable; Chitooligosaccharide; Oxidation-responsive; Self-assembly; “Snowflake-like”;

Novel polymeric macroporous hydrogels were developed to entrap and immobilize lipase. Poly(ethylene glycol) methyl ether acrylate hydrogel was used as the support. The emulsion-gelation method using oil-in-water emulsions was used to simultaneously synthesize the hydrogels and entrap lipase in the randomly distributed, non-interconnected, sphere-like macropores, which were several micrometers in diameter. The lipase, immobilized within the macroporous hydrogel, successfully catalyzed the hydrolysis of triacetin without leakage of lipase or loss of activity during repeated use. The macroporous hydrogel-immobilized lipase exhibited higher activity than the lipase immobilized within a non-porous hydrogel, which indicates entrapment of lipase in the macropores without interference from the polymer and excellent diffusional permeability of macroporous hydrogel to substrate/product species.
Keywords: Polymeric macroporous hydrogel; Enzyme; Immobilization; Lipase; Hydrolysis;

Fabrication of morphology-controlled nano/microstructural polyfluorene in mixed nonsolvent vapor atmospheres by Weibin Bai; Xueqing Xiao; Lifang Cai; Yanlian Xu; Jinhuo Lin (13-18).
Under mixed water and methanol vapor atmospheres, a poly(9,9-dihexylfluorene)/CH2Cl2 solution self-assembles to form various nano/microstructures, such as porous films, spherical segments and microspheres. The water droplet template and the polymer precipitation by methanol were the driving forces that fabricated the patterns. Porous films with different pore sizes were obtained in CS2 solution by altering the mixed vapor atmosphere. Changes in the spreading coefficient and solvent polarity led to the formation of different morphologies. The introduction of miscible solvent vapors in aqueous atmospheres is a facile way to design and fabricate polymeric nano/microstructures.
Keywords: Nano/microstructures; Mixed vapor atmosphere; Porous film; Spherical segment; Microsphere;

Synthesis and investigation of a photosensitive, europium-containing polymer by Shuqi Fan; Xu Fei; Xiuying Wang; Jing Tian; Longquan Xu; Peng Yang; Yi Wang (19-25).
The photosensitive europium-containing polymers display excellent thermal stability, UV light lithograph sensitivity and strong visible fluorescence intensity. The micro patterns fabricated from the europium-containing polymer by direct UV exposure have good chemical resistance.Display OmittedA series of europium complexes containing polymeric reactivity groups have been successfully synthesized using a simple method. Among them, Eu(DBM)2(Phen)(MA), which has the best fluorescence properties and solubility, was polymerized with glycidyl methacrylate (GMA) for use as a novel UV-written polymer material. The Poly (GMA-co-Eu(DBM)2(Phen)(MA)) containing different proportions of europium were prepared, and their spectroscopic properties were investigated in detail. Polymer films with optimum proportions (a molar ratio between GMA and Eu(DBM)2(Phen)(MA) of 15) exhibited good UV light lithograph sensitivities, strong visible fluorescence intensities, high glass transition temperatures (Tg : >170 °C), good thermal stabilities (Td : up to 295 °C) and solvent resistances after crosslinking. Micro patterns with smooth top surfaces were fabricated from the resulting polymer by using direct UV exposure and chemical development.
Keywords: Europium complex; UV-written; Photoluminescence; Crosslinking; Chemical development;

Enzymatic synthesis of collagen peptide–carboxymethylated chitosan copolymer and its characterization by Lihong Fan; Huan Wu; Mi Cao; Xiaoyu Zhou; Min Peng; Weiguo Xie; Shuhua Liu (26-31).
Collagen peptide grafted carboxymethylated chitosan was synthesized by using microbial transglutaminase as bio-catalyst. The catalyzed reaction exhibited high efficiency, selectivity, environmental friendliness. Collagen peptide grafted carboxymethylated chitosan was characterized by Fourier transform infrared spectroscopy. The process conditions were optimized including the reaction time, the reaction temperature, the molar ratio of collagen peptide to carboxymethylated chitosan and the pH value. The different molecular weight, concentration and degree of substitution of collagen peptide–carboxymethylated chitosan had crucial effects on the hydrogen peroxide scavenging activity of collagen peptide–carboxymethylated chitosan. The methyl thiazolyl tetrazolium assay showed that at a suitable concentration collagen peptide–carboxymethylated chitosan with different degree of substitution value could promote L929 mouse fibroblasts effectively. Therefore, the results suggest that collagen peptide–carboxymethylated chitosan could be potential wound dressings for clinical applications.
Keywords: Collagen peptide; Microbial transglutaminase; Antioxidant activity; L929 fibroblast; Cell viability;

RAFT polymerization of acrylic acid (AA) in the presence of low-molecular chain transfer agent (2-(butylthiocarbonothioylthio) propanoic acid and polyacrylate-based backbone bearing multiple butylthiocarbonothioylthio moieties is reported demonstrating successful synthesis of linear pAA with low polydispersity and anionic cylindrical molecular brushes, respectively. Twofold excess of butylthiocarbonothioylthio moieties attached to polyacrylate-based backbone over the initiator was optimal enabling to synthesize graft copolymers with rather low polydispersity (PDI 1.23–1.36) and reasonably high DP of pAA side chains (up to 25). Anionic cylindrical molecular brushes were characterized by SEC with triple detection, DLS, 1H NMR spectroscopy, and potentiometric titration. Thermal transitions and thermal stability of the brush polymers bearing pAA side chains were determined by DSC and TGA.
Keywords: RAFT polymerization; Molecular brushes; Acrylic acid; DLS measurements; Thermal properties;

An efficient route for the synthesis of a strong basic anion exchange fibers is described. In this synthesis route, the commercially available p-chloromethylstyrene was directly grafted onto a polypropylene fiber substrate, which eliminated the need of the highly carcinogenic chloromethyl methyl ether in the chloromethylation of grafting fiber. Several interdependent parameters such as monomer concentration, bath ratio and the influence of solvents on the grafting copolymerization were investigated. The removal efficiency of sugar colorants by the anion exchange fibers was evaluated. The results show that simultaneous irradiation and grafting p-chloromethylstyrene onto polypropylene fiber can obtain a good grafting level under appropriate conditions. The optimal monomer concentration and bath ratio are 40% and 1:30 for a moderate grafting degree and the suitable solvent is toluene. The grafted fiber changed from flexible to rigid. And the prepared material maintains stable before 134.5 °C. The static ion exchange capacity of the synthesized anion exchange fiber is up to 4.72 mmol g−1 and the fiber possesses better ability to remove sugar colorants. The experimental results indicate that the decolorization ratio of the product anion exchange fibers was greater than that of commercial material.
Keywords: Polypropylene fiber; Irradiation grafting; p-Chloromethylstyrene; Anion exchange fiber; Sugar decolorization;

Thermo-reversible Diels–Alder polymerization of difurfurylidene diglycerol and bismaleimide by Hiroyuki Satoh; Aya Mineshima; Taro Nakamura; Naozumi Teramoto; Mitsuhiro Shibata (49-56).
Difurfurylidene diglycerol (DFDG) was synthesized by the acetalization reaction of furfural and diglycerol, both of which can be derived from renewable resources. The 1H and 13C NMR analyses revealed that DFDG is a mixture of stereoisomers. Diels–Alder (DA) polymerization of equimolar amounts of DFDG and 4,4-bismaleimidodiphenylmethane (BMI) at 60 °C for 48 h in chloroform afforded a bio-based linear polyimide (DFDG–BMI) with M w of 5400. Prolonged reaction time resulted in a lowering of molecular weight and an increase of exo/endo DA adduct ratio. The M w of the polyimide obtained by the reprecipitation of DFDG–BMI (pDFDG–BMI) was 7900. The X-ray diffraction and polarized optical microscopic analyses revealed that pDFDG–BMI is a crystalline polyimide. The differential thermal analysis revealed that pDFDG–BMI had a melting temperature at 126 °C, and broad endothermic peaks at around 140–170 °C due to retro DA reaction. The retro DA depolymerization of pDFDG–BMI in N,N-dimethylformamide smoothly proceeded at around 100–120 °C to regenerate the corresponding monomers, as is obvious from the gel permeation chromatographic and 1H NMR spectral analyses.
Keywords: Diglycerol; Furfural; Diels–Alder polymerization; Thermally reversible polymer; Renewable resources;

A new polystyrene-based ionomer/MWCNT nanocomposite for wearable skin temperature sensors by Alessio Giuliani; Massimo Placidi; Fabio Di Francesco; Andrea Pucci (57-62).
The present work outlines the fabrication and testing of a novel skin temperature sensor based on exfoliated and undamaged multi-walled carbon nanotubes (MWCNTs) dispersed in a poly(vinylbenzyl chloride) derivative with triethylamine (PVBC_Et3N). The dispersions were prepared by sonicating MWCNT/PVBC_Et3N mixtures in dimethylformamide for 5 min and the quantification of the MWCNTs dispersed was evaluated by UV–vis spectroscopy investigations and thermogravimetric analyses.The investigations demonstrated the realization of MWCNT/PVBC_Et3N sensors with a resistance sensitivity to temperature close to −0.004 K−1, an absolute value that is comparable to the highest values found in metals. The temperature dependence of the resistance was also found very reproducible in the range 20–40 °C, thus suggesting the possibility of using the MWCNT/PVBC_Et3N system for the fabrication of small wearable temperature sensors for the monitoring of chronic wounds.
Keywords: MWCNTs; Poly(vinylbenzyl chloride) ionomers; MWCNT dispersion; Electrically conducting nanocomposite; Wearable temperature sensor;