Synthesis and Characterization of Poly(N-isopropylacrylamide)-graft-Poly(vinylidene fluoride) Copolymers and Temperature-Sensitive Membranes

Abstract

Molecular modification of ozone-pretreated poly(vinylidene fluoride) (PVDF) via thermally induced graft copolymerization with N-isopropylacrylamide (NIPAAM) in N-methyl-2-pyrrolidone solution was carried out (the NIPAAM-g-PVDF copolymer). The chemical structure and composition of the NIPAAM-g-PVDF copolymers were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. In general, the graft concentration increased with the NIPAAM monomer concentration used for graft copolymerization. Microfiltration membranes were prepared from the NIPAAMg-PVDF copolymers by the phase inversion method. The bulk and surface graft concentrations of the membranes were obtained by elemental analysis and X-ray photoelectron spectroscopy (XPS), respectively. XPS analyses of the copolymer membranes revealed a substantial surface enrichment of the grafted NIPAAM polymer. The pore sizes of the pristine PVDF and the NIPAAM-g-PVDF membranes were measured using a Coulter Porometer. The morphology of the membranes was studied by scanning electron microscopy. The membrane surface composition, mean pore size, and morphology varied with the temperature of the casting bath. For the copolymer membrane cast below the lower critical solution temperature (LCST) of the NIPAAM polymer (∼32 °C), the rate of water permeation increased substantially at a permeate temperature above 32 °C. A reverse permeate temperature dependence was observed for the flux of 2-propanol through the membrane cast above the LCST of the NIPAAM polymer.

Influence of the coagulation‐bath temperature on the phase‐separation process of poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) solutions and membrane structures

“…where V r is the porosity; r water is the density of water (g/mL); m 1 and m 2 are the weights of the membrane in the wet and dry states, respectively (g); and V is the volume of the membrane (cm 3 ).…”

“…In recent years, the temperaturesensitive poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) separation membrane, which has temperature-sensitive performance while retaining the desirable properties of the matrix, has been extensively studied. [1][2][3] However, most of these studies have focused on the preparation, morphology, chemical structure, and temperature-sensitive performance of the flux and rejection of the membrane; little attention has been paid to the membrane-formation mechanism and the process of phase separation. In fact, the phase-separation process influences the morphology and characteristics of the membrane greatly.…”

Rose Bengal‐Grafted Biodegradable Microcapsules: Singlet‐Oxygen Generation and Cancer‐Cell Incapacitation

“…Core-level spectra with fitted peaks of CHI and RB-CHI are shown in Figure 3. For RB-CHI, the C 1s core-level spectra can be curve-fitted with peak components of 285.8 eV for CN species and at 287.4 eV for CONH species, [20] which compare to peaks of CHI at 286.2 eV for www.chemeurj.org CÀO species and at 288.3 eV for C=O species. [21] By comparison to the N 1s spectrum of CHI containing a sole peak component for primary amine, the N 1s core-level spectrum of RB-CHI consists of two peaks at 399.4 and 400.2 eV, which are assigned to amine nitrogen and amide nitrogen, respectively, in excellent agreement with the previously reported XPS investigation.…”

Thermo-Responsive Membranes with Cross-linked Poly(N-Isopropyl-acrylamide) Hydrogels inside Porous Substrates

“…Among the chemical techniques used to prepare thermo-responsive membranes, one of the most common methods is the grafting of thermo-responsive polymers onto porous membrane substrates by different grafting techniques, such as plasma induced grafting [1][2][3][4][5][6][7][8][9][10], UVor 60 Co c-radiation induced grafting [11-17, 30, 31, 43-45], and other chemical grafting methods [20]. Another chemical approach to prepare thermoresponsive membranes involves two steps, i.e., firstly fabricating the thermo-responsive polymers by chemical grafting, and then preparing membranes using the fabricated polymers by the phase inversion method [18,19]. In the case of the physical techniques used for the membrane preparation, the common strategy is to introduce thermo-responsive polymers or binary liquid crystals into porous membrane substrates or onto the substrate surface physically by different methods, such as the vacuum filtration method [21,22], the adsorption method [23,41,42], and the coating method [24].…”