Reactive and Functional Polymers (v.81, #C)

Efficient RAFT polymerization of N-(3-aminopropyl)methacrylamide hydrochloride using unprotected “clickable” chain transfer agents by Patrícia V. Mendonça; Arménio C. Serra; Anatoliy V. Popov; Tamaz Guliashvili; Jorge F.J. Coelho (1-7).
The reversible addition fragmentation chain transfer (RAFT) of N-(3-aminopropyl)methacrylamide hydrochloride (APMA) using unprotected “clickable” chain transfer agents in water/dioxane mixtures is reported. The controlled character of the polymerization was confirmed by the linear increase of the polymer molecular weight with monomer conversion, the narrow molecular weight distribution (Ð  ⩽ 1.1) and by chain extension experiments. The alkyne-terminated PAPMA was further functionalized by “click” chemistry with an azido-functionalized coumarin derivative. The method reported here will be useful for the preparation of novel PAPMA based materials for biomedical applications using a strategy that does not require challenging protection/deprotection steps.
Keywords: N-(3-aminopropyl)methacrylamide hydrochloride; Reversible addition fragmentation chain transfer; “Click” chemistry; Primary amine polymer; Coumarin;

Different amounts of graphene oxide (GO) were incorporated to N,N-dimethylaminoethyl methacrylate (DMAEMA), fabricating a series of pH and temperature dual sensitive PDMAEMA/GO hybrid hydrogels by in situ polymerization. Their microscopic network structures as well as swelling properties and Cr(VI) adsorption were characterized. The equilibrium swelling ratios (ESR) of hydrogels increased significantly with 0.5 wt% GO feeding of DMAEMA amount, and then decreased with further GO loading increasing. All hydrogels showed obvious deswelling when pH value of swelling mediums increased from 5 to 10 gradually. At pH 7, hydrogels revealed slight ESR increment with temperature up to 50 °C, above which obvious deswelling occurred. In pH 8 buffer, 0.5 wt% of GO loading triggered lower critical solution temperature (LCST) to decrease by 3 °C, and 2–7 °C increment was observed when 1–6 wt% of GO was loaded, as compared with that of GO-free PDMAEMA hydrogel. Cr(VI) adsorption of hydrogels was also improved by the introduction of GO to some extent, and the maximum Cr(VI) adsorption of 180 mg/g was realized, indicating that the obtained PDMAEMA/GO hybrid hydrogels possess excellent adsorption performance.
Keywords: N,N-dimethylaminoethyl methacrylate; Graphene oxide; Hydrogel; Swelling property; Cr(VI) adsorption;

Immobilization of rhodamine 6G in calcium alginate microcapsules based on aromatic–aromatic interactions with poly(sodium 4-styrenesulfonate) by Esteban Araya-Hermosilla; Daniel Muñoz; Sandra Orellana; Alejandro Yáñez; Andrés F. Olea; Felipe Oyarzun-Ampuero; Ignacio Moreno-Villoslada (14-21).
Display OmittedImmobilization of rhodamine 6G in calcium alginate microcapsules was achieved using the polyanion bearing negatively charged aromatic groups poly(sodium 4-styrenesulfonate) as complexing agent. The immobilization of the dye by this method finds its basis on the stabilization of the dye/polymer complex by short-range aromatic–aromatic interactions, which are resistant to the cleaving effect of highly concentrated electrolytes. On the contrary, direct immobilization of the dye in the microcapsules resulted unsuccessful due to its high diffusion coefficient in the aqueous medium, and complexation with poly(sodium vinylsulfonate) did not improve the immobilization, since the corresponding complex is based on long-range electrostatic interactions, which are easily cleaved under the high ionic strength conditions of the microcapsule formation reaction. Thus, the present investigation represents a proof of concept on the use of aromatic–aromatic interactions between polyelectrolytes bearing charged aromatic rings and their aromatic counterions as a tool to achieve improved functionalities. The release of the rhodamine 6G/poly(sodium 4-styrenesulfonate) complex from the microcapsules has been investigated as a function of pH and temperature. Coating the microcapsules with chitosan allowed minimizing the release of the dye from the microcapsules.
Keywords: Aromatic–aromatic interactions; Alginate microcapsules; Dye immobilization; Aromatic polymers;

The preparation of a series of oligomeric engineering thermoplastics (PS, PES, PEI and PAI) is reported. 1H and 13C NMR and FT-IR/ATR spectroscopic techniques are combined to determine the chemical structure of the synthetic polymers, which are produced in good yield and purity. GPC measurements show the weight average molecular weight (Mw ) of the synthesised thermoplastics fall in the range 5454–33,866 g mol−1 and display polydispersity indices in the range 1.33–1.82. Glass transition temperatures (Tg ) values measured by DSC, occur between 107 and 257 °C and fall in the pattern PS < PES < PEI < PAI. Molecular simulation is used to probe the structure property relationships displayed by PS and PES and reproduces the elastic properties of PS well within the range of the literature; while the values of PES are less well reproduced. The simulated Tg values of both oligomers agree well with those obtained empirically using DSC.
Keywords: Engineering thermoplastics; Low molecular weight; Thermal analysis; Modelling;

Biodegradable films and sponges of poly(depsipeptide-co-lactide)s with two reactive side-chain groups, poly[(Glc–Asp)-co-LA] and poly[(Glc–Lys)-co-LA], were prepared with entrapped growth factors (bFGF, EGF, and NGF) or models for these growth factors (lysozyme, insulin and lactoferrin) based on their physicochemical similarities. These films and sponges were prepared to evaluate the potential utility of these copolymers as biodegradable scaffolds for tissue engineering. Sustained release of the model proteins from the biodegradable matrices was observed. The cell growth rates on the growth factor-loaded matrices were higher than on those without growth factors and were at the same level as with the addition of native growth factors. The effective differentiation of PC12 cells into nerve-like cells were observed on NGF-loaded copolymer film. These results indicate that the released growth factors maintained their activity and that these copolymers would be good candidates for scaffolds for tissue engineering.
Keywords: Biodegradable polymers; Tissue engineering; Polydepsipeptide; Polylactide; Growth factors;

Ion-conductive and mechanical properties of polyether/silica thin fiber composite electrolytes by Satoki Ishibe; Kodai Anzai; Jin Nakamura; Yuichi Konosu; Minoru Ashizawa; Hidetoshi Matsumoto; Yoichi Tominaga (40-44).
Display OmittedTo enhance the ionic conductivity and mechanical strength of existing polymer electrolytes, we have composited a submicro-scaled non-calcined silica thin fiber (ncl–SiF) in a polyether electrolyte. Composite electrolytes were prepared using polyether and inorganic fillers, including 5 mol% of lithium bis-(trifluoromethane sulfonyl) imide (LiTFSI), and the ionic conductivity and mechanical strength were measured. The submicro-scaled ncl–SiF composite improved the conductivity of the electrolyte, with the highest conductivity exceeding 10−4  S/cm at 30 °C. The stress–strain curves showed significant increases in the Young’s modulus and the stress at break for the composite samples, and the highest value of the Young’s modulus exceeded that of the original 10-fold. Thus, we conclude that highly dispersive ncl–SiF is a highly suitable material for the improvement of ionic conductivity and mechanical strength.
Keywords: Composite polymer electrolyte; Ionic conductivity; Silica thin fiber;

Poly(β,L-malic acid)/Doxorubicin ionic complex: A pH-dependent delivery system by Alberto Lanz-Landázuri; Antxon Martínez de Ilarduya; Montserrat García-Alvarez; Sebastián Muñoz-Guerra (45-53).
Poly(β,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength.
Keywords: Poly(malic acid); Ionic complexes; Doxorubicin complex; pH-dependent; Drug-delivery particle;

A styrene based water soluble polymer containing pendant sulfonated calix[4]arene groups has been synthesized by using free radical polymerization combined with post-polymerization sulfonation chemistry. The monomer 25-(4-vinylbenzyl)-26, 27, 28-hydroxy-calix[4]arene (VBC4A) was prepared in 3 steps: (1) reduction of 4-vinyl benzoic acid to the respective alcohol (2) formation of the bromide by the Appel reaction and (3) synthesis of the respective ether by Williamson O-alkylation reaction with calix[4]arene. Polymerization was accomplished by azobisisobutyronitrile (AIBN) initiated free radical polymerization technique to afford P(VBC4A) with Mn value of 7090 g/mol and moderate polydispersity. The resulting P(VBC4A) was subsequently reacted with acetyl sulfate to afforded the sulfonated polymer. The reaction was followed by nuclear magnetic resonance and infrared spectroscopy, and the results suggest that the sulfonation reaction lead to nearly quantitative functionalization of the calixarene functional polymer. Elemental analysis by X-ray photoelectron spectroscopy confirmed these findings on the degree of sulfonated functionalization. Electro-responsive properties of the sulfonated polymer were studied by cyclic voltammetry and isothermal titration calorimetry in phosphate buffer saline solution. A response to electrochemical stimulus is observed where guest molecules of methyl viologen incorporate and dissociate with P(VBSC4A).
Keywords: Calixarene; Guest–host; Redox potential; Cyclic voltammetry; Isothermal calorimetry;

The adsorptive extraction of oxidized sulfur-containing compounds from fuels by using molecularly imprinted chitosan materials by Adeniyi S. Ogunlaja; Matthew J. Coombes; Nelson Torto; Zenixole R. Tshentu (61-76).
An innovative approach for desulfurisation of fuels is proposed. It relies on the formation of recognition sites, complementary to oxidized sulfur-containing compounds, on cross-linked chitosan microspheres and electrospun chitosan nanofibers using the molecularly imprinted polymer technique. Benzothiophene sulfone (BTO2), dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were used as templates for the preparation of molecularly imprinted polymers (MIPs). The possible molecular interactions between imprinted chitosan adsorbent and oxidized sulfur-containing compounds were investigated by molecular modeling using density functional theory (DFT) and results indicated that interactions took place via hydrogen bonding. The molecularly imprinted polymer adsorbents (cross-linked microspheres and electrospun nanofibers) gave better selectivity for the target sulfonated compounds and the adsorption isothermal studies followed the Freundlich model. Maximum adsorption capacities of 8.5 ± 0.6 mg/g, 7.0 ± 0.5 mg/g and 6.6 ± 0.7 mg/g were observed for model BTO2, DBTO2 and 4,6-DMDBTO2 respectively at 1 mL/h when imprinted nanofibers were employed, and the imprinted microspheres gave maximum adsorption capacity of 4.9 ± 0.5 mg/g, 4.2 ± 0.7 mg/g and 3.9 ± 0.6 mg/g for BTO2, DBTO2 and 4,6-DMDBTO2 respectively. Application of the nanofibers to oxidized hydro-treated fuel under continuous flow adsorption system at 1 mL/h indicated that 84% of sulfur was adsorbed, with adsorption capacity of 2.2 ± 0.2 mg/g.
Keywords: Chitosan; Organosulfur compounds; Nanofibers; Cross-linked microspheres; Molecularly imprinted polymers;

This is the first of a series of reports that probes the polarizabilities of different immobilized ligands in order to build toward a rational design of ion-selective polymer-supported reagents. In this report, the polarizabilities of four ligands on a polystyrene backbone (phosphorylated ethylene glycol (pEG1), ethylene glycol (EG1), sulfonic acid, and dimethylamine (DMA)) are evaluated with Au(III) and Eu(III) as representative of soft and hard ions, respectively. Interactions are followed by the extent of sorption, the effect of acid concentration, band shifts in FTIR spectra, and Langmuir plots. The phosphoryl oxygen, hydroxyl ―OH, and amine show an affinity of Au(III) > Eu(III) while Eu(III) > Au(III) is evident with the sulfonic acid. The P=O stretching frequency shifts from 1263 to 1249 cm−1 upon Au(III) binding. The affinities indicate that oxygen can be considered soft and hard, depending on its microenvironment: neutral oxygen is soft while anionic oxygen may be classified as hard. Though Eu(III) prefers ionic binding with a strong acid ligand, it is also capable of weak binding with a neutral oxygen donor at pH 3 and 4. Sorption is affected by solution acidity despite the absence of ion exchange. Three routes to enhancing ion–interactions thus emerge: preparing single-site ligands whose polarizability matches the targeted metal ion, preparing ligands with multiple binding sites each of which bind weakly on their own, and preparing single-site ligands with dual ion exchange/coordination character.

For this study, we prepared a new type of drug carrier with the characteristics of stimuli-responsive transition and tumor-specific recognition through the co-assembly of two series of amphiphilic block copolymers, poly(ε-caprolactone)-b-poly[triethylene glycol methacrylate-co-N-methacryloyl caproic acid] and poly(ε-caprolactone)-b-poly[triethylene glycol methacrylate-co-N-(2-(methacrylamido)ethyl) folatic amide]. The pH-dependent thermal transition and the content of the targeting ligands of the mixed polymeric micelles are well correlated with the chemical structures and compositions of these two copolymers. Doxorubicin-loaded mixed polymeric micelles are stable at body temperature in the neutral condition for prolonged circulation in blood vessels, and demonstrated rapid drug release at acidic pH levels. The cumulative drug release profiles showed a relatively slow release at pH 7.4, and a quick release of 85% in 3 h at pH 5.3. The cytotoxicity tests against FA-positive (HeLa) and FA-negative (HT-29) tumor cell lines suggest that this mixed polymeric micelle system has potential merits as a controlled and targeted drug delivery system.
Keywords: Drug delivery systems; Functionalization of polymers; Micelles; Stimuli-sensitive polymers;

Synthesis of high performance organic–inorganic composite via click coupling of block polymer and polyhedral oligomeric silsesquioxane by Santosh Kumar Yadav; Sibdas Singha Mahapatra; Hee Jeong Ryu; Hye Jin Yoo; Jae Whan Cho (91-96).
Display OmittedNovel hybrid systems based on poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) and a polyhedral oligomeric silsesquioxane (POSS) have been synthesized via click chemistry. Different compositions of SEBS-functionalized POSS were obtained from the reaction of azide-functionalized styrene units of SEBS with alkyne-functionalized POSS molecules. Characterization of SEBS-functionalized POSS by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy revealed that the POSS molecules were successfully attached to the phenyl group of the SEBS polymer chain following the click reaction. Homogeneous dispersion of POSS molecules in the polymer matrix was demonstrated by scanning electron microscopy. The POSS molecule showed excellent compatibility with polymer matrix, and as a consequence the remarkable enhancement of mechanical properties (breaking stress = 44%, modulus = 285%) and thermal stability for the resulting composite films was achieved. The reinforcing effect is ascribed to both the compatible homogeneous dispersion of POSS in the matrix and the covalent bond between SEBS and POSS molecules arising from the click coupling.
Keywords: POSS; Block copolymer; Composite; Mechanical properties; Click coupling;