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1.
Membranes (Basel) ; 9(8)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374830

RESUMO

In recent years, block copolymer micellar assemblies with the formation of structured nanoparticles have been considered as an emerging technology in membrane science. In this work, the poly(methyl methacrylate)-block-poly(sulfobetaine methacrylate) copolymer was directly synthesized using Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization and self-assembled in a selective medium (2,2,2-trifluroethanol/water). Then, poly(methyl methacrylate)-block-poly(sulfobetaine methacrylate) copolymers were casted onto a commercial PVDF membrane to form a thin porous selective layer. The prepared nanoparticles and the resulting membranes were fully characterized using microscopy methods (SEM and AFM), whereas the membrane performance was evaluated in terms of permeability and the molecular weight cut off. The results from this study demonstrate the preparation of an ultrafiltration membrane made from the assembly of poly(methyl methacrylate)-block-poly(sulfobetaine methacrylate) copolymer micelles on the top of a PVDF membrane in the form of thin film. The copolymer chain orientation leads to a membrane surface enriched in hydrophilic PSBMA, which confers a suitable behavior for aqueous solution filtration on the membrane, while preserving the high chemical and mechanical resistance of the PVDF.

2.
Soft Matter ; 13(39): 7161-7171, 2017 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-28902225

RESUMO

Phase separation of thermo-responsive polymers in solution is a complex process, whose understanding is essential to screen and design materials with diverse technological applications. Here we report on a method based on dynamic light scattering (DLS) experiments to investigate the phase separation of thermo-responsive polymer solutions and precisely define the transition temperature (TPS). Our results are applied on hydroxypropylcellulose (HPC) solutions as an important biosourced green water-soluble polymer. As determined by DLS, the amplitudes of the fast and slow modes of relaxation dynamics evolve as temperature gets closer to the phase transition point eventually leading to phase separation. The evolution of relaxation modes with temperature is markedly different for concentrations below the overlap concentration (c*) (dilute regime), above c* (semi-dilute regime) and above the entanglement concentration (ce). In the three cases though, the fast and slow mode amplitudes undergo a sharp transition in a narrow temperature range, defining accurately the phase separation locus. The results agree with turbidimetric analysis for the phase transition determination but with a better precision. Our results also show that the one-phase dynamics and phase separation dynamics in the two-phase region are only in continuity for c > ce, revealing mechanistic details about the HPC phase separation process. Above TPS we identify a temperature range where the intensity autocorrelation function has a single-exponential shape. In the latter regime, we monitor the growth kinetics of polymer domains and provide clues to rationalize the stabilizing effects of the interfaces leading to the arrested-like phase separation behavior observed for HPC.

3.
J Hazard Mater ; 260: 425-33, 2013 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-23811363

RESUMO

In this paper, original thermosensitive copolymers bearing phosphonic acid groups, namely the poly(N-n-propylacrylamide-stat-2-(methacryloyloxy)methylphosphonic acid) (P(NnPAAm-stat-hMAPC1)) were synthesized, and their sorption properties for three divalent cations (Ni(2+), Ca(2+), Cd(2+)) and one trivalent cation (Al(3+)) have been investigated. The sorption experiments were performed with increasing relative amount of cationic pollution compared to the amount of sorption sites (C(n+)/P ratio) in mono and multi-component solutions to investigate the sorption mechanisms. C(n+)/P proved to strongly affect the sorption capacity and high capacities were obtained for all cations at highest C(n+)/P ratios, reaching one mole of C(sorbed)(n+) per phosphonated moiety. For divalent cations, sorption mechanisms were likely to be described by electrostatic interactions only, whereas for aluminum trivalent cation the sorption not only resulted from electrostatic interactions but also from the formation of coordination binding. The selectivity of the phosphonic acid moieties for aluminum cations was demonstrated, highlighting the interest of P(NnPAAm-stat-(h)MAPC1) for their use for the treatment of metallic pollution from wastewater.


Assuntos
Alumínio/química , Carbono/química , Cátions Bivalentes/química , Ácidos Fosforosos/química , Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Fosfatos/química , Polímeros/química , Soluções , Eletricidade Estática , Fatores de Tempo , Poluentes da Água/análise , Poluentes da Água/química , Purificação da Água/métodos
4.
J Hazard Mater ; 244-245: 507-15, 2013 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-23183346

RESUMO

In order to remove metal ions from wastewaters, thermosensitive copolymers bearing sorption properties toward metal cations were prepared by free radical copolymerization between the N-n-propylacrylamide (NnPAAm) and the (dimethoxyphosphoryl)methyl 2-methylacrylate (MAPC1), followed by a hydrolysis of the phosphonated esters into phosphonic diacid groups ((h)MAPC1). The thermosensitivity and the sorption abilities of the resulting poly(NnPAAm-stat-(h)MAPC1) copolymers were studied. Lower Critical Solution Temperatures (LCST) of these copolymers ranged from 22 °C to 26 °C, depending on the molar ratio of phosphonated monomers and were lower than those obtained with usual poly(N-isopropylacrylamide)-based polymers. The influence of both the temperature and the pH on the sorption properties of the copolymers was evaluated for Ni(2+) cations. The most interesting results were obtained for temperatures around the LCST, i.e. when the proximity of the complexing groups favored the sorption of metallic cations. Concerning the pH effect, the maximum sorption capacity was obtained at pH 7, i.e. in the absence of competition between the sorption of H(+) and Ni(2+) ions on the phosphonic acid groups. The influence of the molar ratio of metal ions and phosphonate moieties was also studied and different sorption mechanisms were proposed.


Assuntos
Níquel/química , Ácidos Fosforosos/química , Poluentes Químicos da Água/química , Acrilatos/química , Adsorção , Polímeros/química , Soluções , Temperatura , Eliminação de Resíduos Líquidos/métodos
5.
Angew Chem Int Ed Engl ; 51(29): 7166-70, 2012 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-22696305

RESUMO

When pressure is applied to dynamic interactive membranes consisting of micelles composed of a triblock copolymer, their morphologies can be fine-tuned. Membranes with a range of porosities are accessible which can regulate and thereby control filtration performance and also display effective autonomous healing.

6.
J Colloid Interface Sci ; 292(2): 413-28, 2005 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-16054637

RESUMO

This study focuses on the relation among hydrodynamics, physicochemical conditions, and floc size. During ortho-kinetic flocculation, the floc size is controlled by a balance between hydrodynamic stress and aggregate strength. Special attention was paid to the influence of a hydrodynamic sequencing on both the aggregate strength and the flocculation processes. Experimental research was conducted in a 1-L jar for two different pH values. The hydrodynamic sequencing was made up of successive slow and rapid mixing periods, and different slow mixing intensities were studied. First, the large floc size was shown to decrease with increasing velocity gradient (G), with an expected trend (d proportional variant epsilon(-1/4)). Then, the aggregate strength was shown to depend on two main factors: the flocculation history and the physicochemical conditions, which control the cohesion forces between primary particles. Finally, flocculation processes are discussed in terms of aggregation and breakup phenomena, with relation to local hydrodynamics and physicochemical conditions.

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