Experimental study of the TEMPO mediated copolymerization of styrene with divinylbenzene

Since the discovery of controlled radical polymerization (CRP) in the early nineties (Georges et al., 1993), an ever increasing activity has been focused on the production of polymers with narrow molecular weight distributions and well-de ned architectures (such as block copolymers, stars or brushes). This work describes an experimental research on the nitroxide-mediated radical polymerization (NMRP) of styrene (S) and divinylbenzenes (DVB) in xylene (X) solution at 130 °C, using the stable radical TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy) as mediator and AIBN (azobisisobutyronitrile) as initiator. Measurements of absolute molecular weights and z-average radius of gyration of the produced copolymers have been performed for different polymerization times using a SEC system with coupled refractive index (RI) and multi-angle laser light scattering (MALLS) detectors.FC

Time programmed feed of semi-batch reactors with non-linear radical copolymerizations: an experimental study of the system styrene+divinylbenzene using SEC/MALLS

Time programmed feed of semi-batch reactors with non-linear radical copolymerizations: an experimental study of the system styrene+divinylbenzene using SEC/MALLSFCT European Commissio

Reversible addition-fragmentation chain transfer copolymerization of styrene/divinylbenzene in aqueous suspension

The Reversible Addition-Fragmentation Chain Transfer (RAFT) copolymerization of styrene (S) and divinylbenzene (DVB) was performed at temperature range 110 to 150 °C in aqueous suspension, using AIBN as thermal initiator and 2-dodecylthiocarbonothioylthio-2-methylpropionic acid (DDMAT) as RAFT agent.inancial support by Fundação para a Ciência e a Tecnologia (FCT), Ministry of Science and Technology of Portugal (Program COMPETE - QCA III) and European Community through FEDER is gratefully acknowledged (project PTDC/EQU-EQU/098150/2008)

Computer simulation aided synthesis of sodium acrylate/acrylic acid superabsorbent polymers

The influence of the synthesis conditions on the end use properties of SAPs was experimentally observed. Initial proportion crosslinker/acrylic acid and degree of neutralization are examples of parameters with strong influence in the performance of these materials. The kinetic model developed is able to capture the main features of SAP production. Ongoing research should allow the prediction of elastic properties of this class of materials.BASF AG, Fundação para a Ciência e a Tecnologia (FCT), Ministry of Science and Technology of Portugal (Program COMPETE - QCA III) and European Community through FEDE

Kinetics of gelation in pH/temperature-sensitive hydrogels synthesis

Kinetics of gelation was experimentally and theoretically studied for different polymerization systems leading to the formation of pH/temperature-sensitive hydrogels. Acrylamide (AAm), N-isopropylacrylamide (NIPA), N,Ndimethylacrylamide (DMA), acrylic acid (AA), methacrylic acid (MAA) were used as main monomers, and N,N’- methylenebisacrylamide (MBAm) as crosslinker.Financial support by Fundação para a Ciência e a Tecnologia (FCT), Ministry of Science and Technology of Portugal (Program COMPETE - QCA III) and European Community through FEDER is gratefully acknowledged (project PTDC/EQU-EQU/098150/2008)

Kinetic modeling of the molecular architecture of cross-linked copolymers synthesized by controlled radical polymerization techniques

Kinetic Modeling of the Molecular Architecture of Cross-Linked Copolymers Synthesized by Controlled Radical Polymerization TechniquesFC

SEC/MALLS measurement of the branched structure of methyl methacrylate + ethylene glycol dimethacrylate copolymers synthesized by atom transfer radical polymerization

In the last few years, atom transfer radical polymerization (ATRP) of acrylate and methacrylate monomers in the presence of a small amount of cross-linker has been investigated in order to produce branched polymers and gels with applications in microelectronics, coatings industries or biomedicine (Wang and Zhu, 2005; Gao et al., 2007). In this context, it is being explored the production by ATRP of branched/crosslinked polymers with a lower degree of heterogeneity than that obtained by conventional free radical polymerization (FRP). This work reports an experimental study on the ATRP of methyl methacrylate (MMA) + ethylene glycol dimethacrylate (EGDMA) initiated by MBPA (methyl -bromophenylacetate) and mediated by copper bromide (CuBr) ligated with HMTETA (1,1,4,7,10,10- hexamethyltriethylenetetramine). The synthesized copolymers were analyzed by size exclusion chromatography (SEC) with simultaneous detection of refractive index (RI) and multi-angle laser light scattering (MALLS) signals. Important details of the molecular architecture of these materials can therefore be measured, namely absolute molecular weights and z-average radius of gyration. Different experimental runs were performed in order to investigate the influence of the operating conditions (e.g. temperature and initial molar ratios MMA/EGDMA/MBPA/CuBr/HMTETA) on the structure of the products.FC

Synthesis and characterization of pH-sensitive acrylamide/acrylic acid hydrogels

Different samples of pH-sensitive hydrogel particles were produced using inverse-suspension, leading to the identification of the influence on their end-use properties of the degree of neutralization of AA monomer and the initial composition of the terpolymerization system which are therefore the key parameters of the synthesis. These studies were also used to develop a kinetic model improving the design of production processes of tailored smart polymers.Fundação para a Ciência e a Tecnologia (FCT), Ministry of Science and Technology of Portugal (Program COMPETE - QCA III) and European Community through FEDE

Kinetic modeling of the inverse suspension production of acrylic gels using in line FTIR-ATR monitoring and off-line SEC/RI/MALLS product characterization

This work describes the production of acrylic gels in a batch stirred reactor at 1.5 dm3 scale. Inverse suspension technique is used within this purpose. Paraffin (P) was used in the continuous phase and polymer networks were synthesized in the dispersed phase containing water (W) dissolved acrylic acid (AA), trimethylolpropane triacrylate (TMPTA), used as crosslinker, and 2,2’-azobis(2-methylpropionamidine) dihydrochloride (V50) as a free radical initiator.BASF, FCT, European Communit

Kinetic studies on RAFT inverse-suspension smart hydrogels formation using a tetra detector array

Temperature/pH stimuli-responsive hydrogel particles were synthesized using inverse-suspension polymerization in batch stirred reactor. Different water soluble comonomers were present in the initial mixture (namely N-isopropylacrylamide and acrylic acid) as well as crosslinkers with different functionalities (bi-, tri- and tetrafunctional) so that their effect on the network crosslinking density could be seen. Different operating conditions such as polymerization temperature (in the range 20 to 70 °C), monomers dilution, neutralization and the inilial ratios 01 co-monomers and monomers/crosslinker were also tried. Classical Iree-radical polymerization (FRP) and RAFT polymerization (e.g. using 4-cyano-4-phenylcarbonothioylthio-pentanoic acid) were compared in order to put into evidence the impact of the polymerization mechanism on the hydrogel molecular architecture. Sampling at different polymerization limes allowed the study of the kinetics of gel formalin through the analysis by SEC of the soluble phase. RI, LALLS, Intrinsic Viscosity and UV signals were simultaneously measured using a tetra-detector array, thus yielding absolute molecular weight, branching factors, hydrodynamic radius and radius 01 gyration. The performance 01 hydrogel beads was assessed through drug delivery tests triggered by changes in the environmental temperature/pH. Aiming at the development of tools hopefully useful for the design of such advanced materials, a general kinetic approach (Chem. Eng. Sci. 2005, 60, 423) was used to carry out modeling studies including consideration of finite loop formation reactions.FCT and FSE (Programa Operacional Potencial Humano/POPH), project PTDC/EQU-EQU/098150/2008 (Ministry of Science and Technology of Portugal/Program COMPETE – QCA III/and European Community/FEDER), Marie Curie Initial Training Network ‘‘Nanopoly’’ (Project: ITN-GA-2009-238700)