Equilibrium concentration profiles of physically end tethered polystyrene molecules at the air-polymer interface

Hopkinson, Ian; Kiff, F.T.; Richards, Roy J.; Bucknall, David G.; Clough, A.S.

doi:10.1016/s0032-3861(96)00482-x

Cited by 39 publications

(46 citation statements)

References 31 publications

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“…Some of the detached polymer becomes adsorbed at the air-polymer interface as a surface excess layer and each interfacial excess layer (air and silicon) is in equilibrium with the bulk content of NDPSF. The adsorption isotherm for deuteriopolystyrene with one end functionalised by the fluorosilane used mixed with hydrogenous polystyrene has been obtained earlier [12]. The relevant thermodynamic parameter to compare is the normalised surface excess and from the isotherm obtained in the earlier work it appears that for a bulk volume fraction of 0.05 to 0.09 we should have 15 ≤ z * /Å ≤ 20 at equilibrium at the air-polymer interface.…”

Section: Approach To Equilibriummentioning

confidence: 91%

“…The broad peaks in the regions −50 < z/Å < 150 and 400 < z/Å < 700 correspond to the excesses of NDPSF present at the vacuumpolymer surface and the polymer-substrate interface of the film. The width of these peaks is determined by the instrument resolution, and for these samples the magnitude of the interfacial excess is obtainable but the detailed distribution of the NDPSF excess layer normal to each interface cannot be obtained [12]. This latter aspect has been explored using neutron reflectometry.…”

Section: Nuclear Reaction Analysis Datamentioning

confidence: 99%

“…There has been a variety of end groups in polymers used to generate such self-assembled layers [6][7][8][9][10][11][12] and by virtue of their grafting, chemical or physical, to an interface these polymers can be described as telechelic. The objectives of the majority of these investigations has chiefly been the examination of polymer brush layers, comparison with the predictions of theory and evaluation of the kinetics of formation of the brush like layer.…”

Section: Introductionmentioning

confidence: 99%

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Partitioning of a heterotelechelic polystyrene to separate interfaces of thin films

Richards

Thompson

Bucknall

et al. 2001

The European Physical Journal E

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Heterotelechelic deuteropolystyrenes have been synthesised with a tertiary amine functionality at one end and a fluorocarbon group at the other end of the polymer chain. A layer of this polymer, circa 120Å thick, has been attached to the surface of a silicon substrate and subsequently covered with a much thicker layer of hydrogenous polystyrene. The combination has then been annealed at 413 K under vacuum for defined times and the subsequent distribution of the deutero heterotelechelic polymer determined using nuclear reaction analysis and neutron reflectometry. The influences of annealing time, molecular weight and thickness of the hydrogenous polymer have been examined. Nuclear reaction analysis showed that an excess of the heterotelechelic polymer formed at both interfaces with a larger excess remaining at the substrate-polymer interface. When the molecular weight of the hydrogenous polymer is lower than that of the deuteropolymer, the deutero layer is initially swollen by the hydrogenous polymer but the thickness then decreases as deutero polymer becomes detached from the silicon substrate and an additional excess layer is eventually formed at the vacuum-polymer surface. When the molecular weight of the hydrogenous polymer is higher, there is an initial shrinkage of the deuteropolymer layer, but the original thickness (∼ radius of gyration of the deuteropolymer) is regained on prolonged annealing. There is no evidence for bridging between the two interfaces by the heterotelechelic polymer. After five days annealing the volume fraction distribution of the deuteropolymer at the silicon substrate was well described by a self-consistent field model where the only adjustable parameter was the sticking energy of the tertiary amine group to the silicon substrate for which a value of 8 kBT was obtained. Comparison of the dependence of the equilibrium layer thickness of the deuteropolymer on the equilibrium grafting density at the silicon surface with the predictions of scaling theory for brush-like polymer layers suggested that the grafted molecules were in the ideal, unperturbed brush region.

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Section: Approach To Equilibriummentioning

confidence: 91%

Section: Nuclear Reaction Analysis Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Partitioning of a heterotelechelic polystyrene to separate interfaces of thin films

Richards

Thompson

Bucknall

et al. 2001

The European Physical Journal E

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“…17 The low energy end group À ÀCF 3 that diffused preferentially to the air-side surface has also been documented by other analysis techniques, such as neutron reflection (NR), nuclear reaction analysis, static secondary ion mass spectroscopy. [18][19][20][21] In addition, since a À ÀCF 3 component in the S-PS-(CF 3 ) 2 /PS-H membrane is very hydrophobic, its localization at the air-side surface makes the membrane surface more thermodynamically stable. 17 The relatively constant surface free energy means that the amount of S-PS-(CF 3 ) 2 at the air-side surface was almost saturated.…”

Section: Surface Characterizationmentioning

confidence: 99%

Pervaporation performance of polystyrene membrane surface with perfluoroalkyl groups

Ni¹,

Zhang²,

Wang³

et al. 2007

J of Applied Polymer Sci

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ABSTRACT:Research on the effect of various chemical groups on the pervaporation performance of membranes was very important for understanding the separation phenomenon. In this article, a polystyrene membrane with À ÀCF 3 groups on its surface was prepared by casting normal polystyrene (PS-H) solution with small-molecular-weight a,x-fluoroalkyl-terminated polystyrene (S-PS-(CF 3 ) 2 ) on a glass plate. The amount of À ÀCF 3 groups on the surface was adjusted by changing S-PS-(CF 3 ) 2 content, which was documented by X-ray photoelectron spectroscopy analysis, surface energy, and contact angle measurements. The effect of S-PS-(CF 3 ) 2 content on separation performance of S-PS-(CF 3 ) 2 /PS-H blend membranes for ethanol/water mixture was investigated. The results showed that water concentration in the permeate decreased with increasing S-PS-(CF 3 ) 2 content; however, the permeation rate did not change until the S-PS-(CF 3 ) 2 content was increased to 1 wt %. The reason for this was attributed to the fact that a small amount of S-PS-(CF 3 ) 2 enables a simple surface modification of the membrane keeping its inner structure relatively unchanged. This was confirmed by swelling degree measurements and other experiments. Comparison with our previous work showed that the À ÀCF 3 groups on the surface lowers the water permselectivity of the polystyrene membranes, whereas the À ÀCOOH groups enhance the water permselectivity. However, neither hydrophobic À ÀCF 3 nor hydrophilic groups on the membrane surface appeared to have any influence on flux.

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“…The behaviour of end functionalised polymers carrying single fluoroalkyl (CF) group at surfaces and interfaces has been studied by several research groups, although in the main it has been shown that a single CF group has a very limited impact upon surface properties and the use of multiple CF end groups presents a more efficient and effective approach to efficient surface modification [19][20][21][22][23][24][25][26] . Thus, we have previously demonstrated that the concept of using low concentrations of end functionalized polymer additives carrying multiple (2-4) CF groups can be very effective for the modification of surface properties and offer the possibility of generating PTFE like surface properties at very low loadings (considerably less than 1.0% (w/w) CF in the bulk).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterisation of end-functionalised poly(N-vinylpyrrolidone) additives by reversible addition–fragmentation transfer polymerisation

et al. 2013

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(2013) 'Synthesis and characterisation of end-functionalised poly(N-vinylpyrrolidone) additives by reversible additionfragmentation transfer polymerisation.', Polymer chemistry., 4 (9). pp. 2815-2827. Further information on publisher's website:http://dx.doi.org/10.1039/c3py00041aPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. We describe herein the synthesis of a series of multi-end functionalized poly(Nvinyl pyrrolidone) (PVP) additives bearing two or three C 8 F 17 fluoroalkyl (CF) groups, designed as additives to modify surface properties. The PVP additives were prepared by reversible addition-fragmentation transfer (RAFT) polymerization, with end functionality imparted via the use of CF functionalized chain transfer agents (CTAs). The resulting PVP additives, when used in modest quantities dispersed in thin films of an unmodified PVP matrix significantly reduce the surface energy, rendering their surfaces more hydrophobic and lipophobic. This is achieved by virtue of the low surface energy of the pendant C 8 F 17 end groups which cause the additive to spontaneously surface segregate during the spin coating process. The resulting thin films have been characterized by static contact angle measurements using dodecane as the contact fluid, and the impact of additive molecular weight, matrix molecular weight, the number of CF groups and additive concentration upon surface properties is reported herein. Significant increases in contact angle were observed with increasing additive concentration, up to a critical aggregation concentration (CAC). Increasing the number of CF groups (from 2 to 3); reducing additive molecular weight or increasing the matrix molecular weight, resulted in increased contact angles and hence surface lipophobicity. Rutherford backscattering (RBS) analysis was performed on films containing varying concentrations of additive, in order to quantitatively measure the nearsurface fluorine concentration of these films. The results of these experiments were in excellent agreement with those obtained by contact angle analysis, confirming the surface activity and low surface energy of the additives.

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Equilibrium concentration profiles of physically end tethered polystyrene molecules at the air-polymer interface

Cited by 39 publications

References 31 publications

Partitioning of a heterotelechelic polystyrene to separate interfaces of thin films

Partitioning of a heterotelechelic polystyrene to separate interfaces of thin films

Pervaporation performance of polystyrene membrane surface with perfluoroalkyl groups

Synthesis and characterisation of end-functionalised poly(N-vinylpyrrolidone) additives by reversible addition–fragmentation transfer polymerisation

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