Thermo-sensitive switching membranes regulated by pore-covering polymer brushes

Yang, Biao; Yang, Wantai

doi:10.1016/s0376-7388(03)00182-0

Cited by 100 publications

(52 citation statements)

References 25 publications

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“…Therefore, the present membranes using PS-b-PNIPAM-b-PS block copolymer films exhibit reversed thermal behavior as compared to most of the previously reported stimuli-responsive membranes, in which permeability is reduced in cooling below the transition temperature. 47,48,50,51,53,56 The latter membranes are usually designed using different concepts, where the stimuliresponsive polymer is often directly grafted to pore walls. In such a scenario, in the swollen state the stretched stimuliresponsive polymer brushes fill the pores and essentially close the channels.…”

Section: Ps-b-pnipam-b-ps Structures In Bulkmentioning

confidence: 99%

Phase Behavior and Temperature-Responsive Molecular Filters Based on Self-Assembly of Polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene

et al. 2007

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This work describes the synthesis of temperature-responsive polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene triblock copolymers, i.e., PS-b-PNIPAM-b-PS, their self-assembly and phase behavior in bulk, and demonstration of aqueous thermoresponsive membranes. A series of PS-b-PNIPAM-b-PS triblock copolymers were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The hydrophobic PS end blocks were selected to form the minority component, whereas the temperatureresponsive PNIPAM midblock accounted for the majority component. The self-assembly and phase behavior in bulk of PS-b-PNIPAM-b-PS as well as selected blends with low molecular weight PNIPAM homopolymers were studied using transmission electron microscopy (TEM). Classical lamellar, cylindrical, spherical, and bicontinuous double gyroid morphologies were observed in the dried state. In aqueous solutions, the glassy PS domains act as physical cross-links, and hydrogels were therefore formed. The bulk block copolymer morphology had a strong effect on the degree of swelling in aqueous solutions upon cooling below the coil-globule transition temperature of the PNIPAM midblock. Bulk compositions with spherical PS domains and PNIPAM continuous phase swelled in water up to 58 times by weight, whereas composition having cylindrical PS domains or bicontinous gyroid structure in bulk swelled 20 or 10 times by weight, respectively. Finally, lamellar compositions did not show any swelling. Composite membranes for separation studies were prepared by spin-coating thin films of PS-b-PNIPAM-b-PS on top of meso/macroporous polyacrylonitrile (PAN) support membrane. The permeability was measured as a function of temperature using aqueous mixture of poly(ethylene glycol) (PEG) with several well-defined molecular weights. The permeability showed a temperature switchable on/off behavior, where higher permeability is obtained below transition temperature of PNIPAM, and the molecular cutoff limits for the PEG molecules are surprisingly lowsbetween 108 and 660 g/mol. The results encourage to further develop and optimize these materials for responsive nanofiltration applications.

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Section: Ps-b-pnipam-b-ps Structures In Bulkmentioning

confidence: 99%

Phase Behavior and Temperature-Responsive Molecular Filters Based on Self-Assembly of Polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene

et al. 2007

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“…25 Several surface 'grafting from' techniques have been reported in the literature, including chemical grafting, 25 plasma, 24,26 radiation 13,19,27,28 and photoinduced grafting. 29,30 A previously reported plasma-induced grafting technique 24 was chosen for the grafting of PNIPAM to the PCTEPMs because it presented several advantages to incorporating the desired properties into the PC membrane. Plasma-induced grafting allows control over the location of the grafting of the PNIPAM chains, either on the membrane surface or on the walls of the pores.…”

Section: Synthesis Pathway To Incorporate Pnipam Into Pctepmsmentioning

confidence: 99%

Bioinspired synthesis of optically and thermally responsive nanoporous membranes

Morones‐Ramírez

2013

NPG Asia Mater

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The development of porous membranes that can rapidly change flow rates in response to external, noninvasive stimuli has broad technological applications for areas ranging from biomedical devices to architecture. Environmentally responsive membranes have a fundamental role in the development of devices used in chemical sensors, biological sorters, sequencing, separations, high-throughput medical devices and labs on a chip. The design and engineering of these responsive porous membranes have been achieved through the coupling of porous membranes with polymeric materials that can change their physical conformation in response to pressure, heat, pH or different chemical entities. Inspired by the phototropic growth of coleoptiles and the light-mediated mechanism that plants use to open their stomata, in this work, light-responsive porous membranes were engineered, mathematically modeled and synthesized. This biologically inspired approach led to a state-of-the-art design technique and a device that outperforms its natural counterpart and is capable of reversibly controlling flow rates from 0.001 to 0.035 ml s À1 cm À2 in less than a few minutes using the noninvasive stimulus of light. We envision that the polymeric responsive membranes and the platform synthesis technique employed in this manuscript for their fabrication could be utilized in a broad range of applications and will have a great impact on the fields of fluid handling, biomedical high-throughput devices, sensors, medicine and other fields of chemistry, biology and mechanical engineering.

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“…However, as the extended PNIPAAm chains are heated above LCST, the polymer chains collapse abruptly and phase transition occurs. 11,12 Application of PNIPAAm or PNIPAAm copolymers to modification of surfaces of some materials, such as silica particle, 13 glass 14 and polymer membrane, 15 was extensively reported in literature, and these modified materials showed thermo-sensitive properties.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Temperature‐responsive Porous Monoliths

Zhang

Qi²,

Xiao

et al. 2009

Chin. J. Chem.

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A new temperature-responsive porous monolith has been prepared by surface-initiated activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) grafting poly(N-isopropylacrylamide) (PNIPAAm) within the pores of the porous polymer monolith. The grafting copolymerization was carried out by a method based on a continuous flow-through technique without special deoxygenation procedure needed in the general ATRP. The addition of ascorbic acid could counteract the oxidation effect of oxygen diffusing into the reaction system. The resulting grafted monolith was characterized by a mercury intrusion method and the size of macropore was 3.65 µm, which was suitable for flow through the monolith for HPLC. The thermally responsive property of the grafted monolith was evaluated by HPLC using steroids with various hydrophobicities as probes. Through determination of retention factor of each steroid on the grafted monolith at different temperatures using water as mobile phase, it was found that the slope of the plot of retention factor of each steroid versus the temperature changed around the low critical solution temperature (LCST, 32 ℃) of PNIPAAm in water. It was relative to the grafted PNIPAAm temperature sensitivity that a hydrophobic and hydrophilic alternation would take place around its LCST. Based on this thermally responsive property, the grafted monolith was used as stationary phase for HPLC and to separate the steroids using water as mobile phase by changing the column temperature. As a mobile phase, water is much better than organic solvents concerning the environment.

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Thermo-sensitive switching membranes regulated by pore-covering polymer brushes

Cited by 100 publications

References 25 publications

Phase Behavior and Temperature-Responsive Molecular Filters Based on Self-Assembly of Polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene

Phase Behavior and Temperature-Responsive Molecular Filters Based on Self-Assembly of Polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene

Bioinspired synthesis of optically and thermally responsive nanoporous membranes

Preparation and Characterization of Temperature‐responsive Porous Monoliths

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