Molecular Engineering, Synthesis and Testing of Water Compatible Smart Polymers

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Kinetic Modeling of the Suspension Copolymerization of Styrene/Divinylbenzene with Gel Formation

Publication . Gonçalves, Miguel A.D.; Pinto, Virgínia; Dias, Rolando; Costa, Mário Rui

Experimental and theoretical studies concerning the suspension copolymerization of styrene with divinylbenzene are reported. Experiments were carried out in a batch stirred reactor, at 1.2 dm3 scale, and extended beyond gelation in order to synthesize insoluble material. Looking for real time information concerning the building process of such materials, these polymerizations were In-line monitored using a FTIR-ATR immersion probe. Polymer samples collected before and after gelation were Off-line characterized using a SEC/RI/MALLS system allowing the measurement of monomer conversion, average molecular weights, MWD and also the z-average radius of gyration. The weight fraction of insoluble material (gel) was measured for samples with different reaction times. The experimental program has included the study of the influence of key polymerization parameters on the dynamics of gelation and some properties of the resulting networks, namely the initial mole fraction of crosslinker and the initial proportions between monomers and inert diluent. Variable n-heptane/toluene mixtures were used within this purpose. These experimental observations were complemented with theoretical studies using a general kinetic approach allowing the prediction of MWD and z-average radius of gyration before and also after gelation. Comparison of the experimental measurements with these predictions is being exploited to develop modeling tools useful for the design of operating conditions allowing the improvement of the performance of the final products.

2011Conference object

Restricted access

Gel formation in aqueous suspension nitroxide-mediated radical co-polymerization of styrene/divinylbenzene

Publication . Gonçalves, Miguel A.D.; Pinto, Virgínia; Dias, Rolando; Costa, Mário Rui; Aguiar, Leandro G.; Giudici, Reinaldo

Results from an experimental study concerning gel formation with nitroxide-mediated radical polymerization (NMRP) of styrene (S) and divinylbenzene (DVB) in aqueous suspension are reported. Influence of certain polymerization parameters on the dynamics of network formation was measured, namely the polymerization temperature and initial composition. Soluble polymer formed at different polymerization times was analyzed by size exclusion chromatography (SEC) with refractive index (RI) and multi angle laser light scattering (MALLS) detection. Concentration of pendant double bonds (PDB) was quantified by means of ICl titration and the morphology of the S/DVB particles was inspected by SEM. Incidence of cyclizations was assessed and the improvement of network homogeneity when using NMRP/FRP is discussed.

2013Journal article

Restricted access

Dynamics of network formation in aqueous suspension RAFT styrene/divinylbenzene copolymerization

Publication . Gonçalves, Miguel A.D.; Pinto, Virgínia; Dias, Rolando; Hernándes-Ortiz, Júlio; Costa, Mário Rui

Experimental studies concerning the RAFT copolymerization of styrene and commercial divinylbenzene were performed in order to assess the use of controlled radical polymerization for the production of non-conventional polymer networks. Aqueous suspension polymerizations were carried out in stirred batch reactor and changes of a few operation parameters were tried in order to assess their effect on key product properties: reaction temperature, initial ratio monomer/RAFT agent, monomer dilution in the organic phase and crosslinker content in the monomer mixture were changed along the experimental program. Polymerizations were extended beyond the gel point in order to synthesize gel beads. The effect of different commercially available RAFT agents (e.g. S-thiobenzoyl thioglycolic acid and two trithiocarbonates) on network process formation was also studied. Dynamics of gel formation was measured using size exclusion chromatography with refractive index and light scattering detection. Iodine chloride titration yielded pendant double bonds concentration. In-line and offline FTIR-ATR measurements were also performed in order to obtain information concerning the kinetics of formation and final structure of the gels.

2013Conference object

Restricted access

Kinetic modeling of the aqueous copolymerization of acrylamide with N,N’-methylenebisacrylamide

Publication . Pinto, Virgínia; Gonçalves, Miguel A.D.; Dias, Rolando; Costa, Mário Rui

This research reports kinetic modeling studies concerning the synthesis of PAAm and acrylamide/N,N’-methylenebisacrylamide (AAm/BAAm) hydrogels, in a 2.5 L batch reactor, considering aqueous solution and water in oil inverse suspension polymerizations.

2011Conference object

Open access

Stimuli-responsive hydrogels synthesis using free radical and RAFT polymerization

Publication . Gonçalves, Miguel A.D.; Pinto, Virgínia; Costa, Rita Alexandra Santos da; Dias, Rolando; Hernándes-Ortiz, Júlio; Costa, Mário Rui

Temperature and pH stimuli-responsive hydrogel particles were synthesized using inverse-suspension polymerization in batch stirred reactor. Different water soluble co-monomers were present in the initial mixture (e.g. N-isopropylacrylamide and acrylic acid) as well as crosslinkers with different functionalities. Different operating conditions such as polymerization temperature, monomers dilution, neutralization and the initial ratios of co-monomers and monomers/crosslinker were also tried. Hydrogel particles were produced considering classical free-radical polymerization (FRP) and also RAFT polymerization. Commercially available RAFT agents 4-cyano-4-phenylcarbonothioylthio-pentanoic acid (CPA), 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) and cyanomethyl dodecyl trithiocarbonate (CDT) were alternatively used. Sampling at different polymerization times allowed the study of the kinetics of polymerization through the analysis by SEC of the soluble phase. A tetra-detector array with simultaneous detection of refractive index, light scattering, intrinsic viscosity and ultra-violet signals was used in these studies. Usefulness of in-line FTIR-ATR monitoring to study the building process of such networks was also assessed. The performance of hydrogel beads was studied through drug delivery tests triggered by changes in the environmental temperature and pH. This research aims to contribute for the elucidation of the connection between the synthesis conditions, molecular architecture and properties/performance of such advanced materials.

2013Conference object

Open access