Influence of solvent on the network structure formed by free radical polymerization of tri-ethylene glycol dimethacrylate: A dielectric study

Molecular mobility of a series of tri-ethylene glycol dimethacrylate (TrEGDMA) samples polymerized with different amounts of ethyl acetate up to 40% (w/w) as diluent was investigated by dielectric relaxation spectroscopy. In the first measuring scan, the samples show three secondary relaxation processes: a γ process related to the twisting motions within the ethylene glycol moiety as found in the unreacted monomer, a β process assigned to hindered rotations of carboxylic groups residing in non-bonded ends of the monomers linked to the network only by one side of the molecule; and additionally, at higher temperatures, a third process was detected designated as βpol, ascribed to a π flip of the ester unit accompanied by a restricted main chain rearrangement. While the γ and the βpol processes remain in the second scan, the β relaxation goes to extinction due to post-polymerization that took place at the highest temperatures scanned in the previous run, leading to complete polymerization of the network. The strength of γ and β relaxation measured in the first scan increases with the amount of solvent present in the initial mixture, nevertheless, in any case, β relaxation completely disappears in the second scan. © 2009 Elsevier B.V. All rights reserved

Poly[(vinylidene fluoride)-co-trifluoroethylene] Membranes Obtained by Isothermal Crystallization from Solution

Electroactive macroporous poly[(vinylidene fluoride)-co-trifluoroethylene] membranes have been produced by solvent evaporation at room temperature, starting with a diluted solution of the copolymer in dimethylformamide. The pore architecture consists of interconnected spherical pores. This architecture is independent of the membrane thickness. The thickness of the membranes ranges from a few to several hundred mu m, using spin coating and evaporation in static conditions, respectively. The pore structure is explained by a spinodal decomposition of the liquid/liquid phase separation and crystallization in the copolymer-rich phase.The authors thank the Portuguese Foundation for Science and Technology (FCT) for grants PTDC/CTM/73030/2006, PTDC/CTM/69316/2006, and NANO/NMed-SD/0156/2007. V.S. thanks the FCT for the SFRH/BPD/63148/2009 grant. J.L.G.R. acknowledge the support from the Spanish Ministry of Education through project no. MAT2007-66759-C03-01 [including the FEDER financial support and funding in the Centro de Investigacion Principe Felipe in the field of Regenerative Medicine through the collaboration agreement from the Conselleria de Sanidad (Generalitat Valenciana), and the Instituto de Salud Carlos III (Ministry of Science and Innovation)]

Covalently Grafted Peptides to Decellularized Pericardium: Modulation of Surface Density

: The covalent functionalization of synthetic peptides allows the modification of different biomaterials (metallic, polymeric, and ceramic), which are enriched with biologically active sequences to guide cell behavior. Recently, this strategy has also been applied to decellularized biological matrices. In this study, the covalent anchorage of a synthetic peptide (REDV) to a pericardial matrix decellularized via Schiff base is realized starting from concentrated peptide solutions (10-4 M and 10-3 M). The use of a labeled peptide demonstrated that as the concentration of the working solution increased, the surface density of the anchored peptide increased as well. These data are essential to pinpointing the concentration window in which the peptide promotes the desired cellular activity. The matrices were extensively characterized by Water Contact Angle (WCA) analysis, Differential Scanning Calorimetry (DSC) analysis, geometric feature evaluation, biomechanical tests, and preliminary in vitro bioassays

Physicochemical properties of poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blend membranes for lithium ion battery applications : influence of poly(ethylene oxide) molecular weight

Polymer blends based on poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide), P(VDF-TrFE)/PEO, with different PEO contents and molecular weights have been prepared for use as Li-ion battery separator membranes. The electrolyte uptake strongly depends on PEO content within the polymer blend. Thermal, mechanical and electrical properties of the membranes are dependent both on PEO content and molecular weight. A thermal degradation mechanism is also proposed as PEO content has a large influence on the activation energy and thermal degradation of P(VDF-TrFE). After electrolyte uptake, all polymer blends exhibit high ionic conductivity at room temperature, the highest value being 0.7 mS cm− 1 which was obtained for the 40/60 membrane with PEO with Mw = 10 kDa. From the point of view of lithium-ion battery application, polymer blends with 10 kDa molecular weight PEO are more adequate due to its excellent mechanical properties and high ionic conductivity.This work is funded by FEDER funds through the "Programa Operational Factores de Competitividade - COMPETE" and by national funds by FCT - Fundacao para a Ciencia e a Tecnologia, project references Project PTDC/CTM/69316/2006, NANO/NMed-SD/0156/2007 and Pest-C/QUI/UI0686/2011 and grant SFRH/BD/82411/2011 (D.M.C.), SFRH/BD/68499/2010 (C.M.C.) and SFRH/BD/66930/2009 (J.N.P.). The authors also thank funding from Matepro - Optimizing Materials and Processes, "ref. NORTE-07-0124-FEDER-000037", co-funded by the "Programa Operacional Regional do Norte" (ON.2 - O Novo Norte), under the "Quadro de Referencia Estrategico Nacional" (QREN), through the "Fundo Europeu de Desenvolvimento Regional" (FEDER). CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund