Chain dimensions in free and immobilized brush states of polysulfobetaine in aqueous solution at various salt concentrations

Abstract

Abstract. The chain dimensions of free and immobilized polysulfobetaine in aqueous solution at various salt concentrations were investigated by size-exclusion chromatography with multiangle light scattering and neutron reflectivity measurement, respectively. The dependence of the z-average mean square radius of gyration (<S 2 > z 1/2 ) on the weight-average molecular weight (M w ) of free poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate) (MAPS) in aqueous solution at salt concentrations of 74, 100, 200, and 500 mM was described by the perturbed wormlike chain model using the chain stiffness parameter λ -1 , the molar mass per unit contour length M L , and the excluded volume effect B. B increased from 0 to 1.8 nm with increasing salt concentration to 500 mM due to the screening of attractive electrostatic interaction between ammonium cations and sulfonyl anions by salt ions. The swollen structure of the poly(MAPS) brush in D 2 O changed from a shrunken state to a relatively extended state with increasing salt concentration from 0 to 500 mM NaCl/D 2 O solution. The thickness of the swollen poly(MAPS) brush in 500 mM NaCl/D 2 O was 9.0 times greater than 2<S 2 > z 1/2 of free poly(MAPS) due to high osmotic pressure generated by the excluded volume effect of densely grafted polymer chains.

Chain dimension of polyampholytes in solution and immobilized brush states

“…The M w and MWD of the fractionated samples were determined by size-exclusion chromatography measurement using an aqueous NaCl solution at C s ¼0.2 M as an eluent calibrated with a series of corresponding polymers as a standard. 12 The values of M w and M w /M n of free PMAPS were determined to be 2.47Â10 5 g mol À1 and 1.18, respectively. The values of M w and M w /M n of free PMPC were determined to be 2.34Â10 5 g mol À1 and 1.12, respectively.…”

“…Previously, neutron reflectometry at the polyelectrolyte brushes/ deuterium oxide interface was used to characterize the swollen structure of PMAPS 11,12 and PMPC 13 brushes. However, the neutron scattering length density profile provided only an ambiguous estimate of the internal structure of the brushes in an aqueous solution with a large molecular weight distribution (MWD) because the average height of the brush increases with polydispersity, whereas the average stretching in the brush decreases.…”

Surface and Interface Analyses of Polymer Brushes by Synchrotron Radiation

“…4) Likewise, X-ray or neutron reflectivity is employed for the estimation of the density profile in depth direction. 5,6) In contrast, in the case of the polymer brushes grafted on particles, dynamic light scattering (DLS) and small angle Xray scattering (SAXS) provide, respectively, the hydrodynamic radius and the gyration radius and the density profile from the surface of particles. 7,8) As mentioned in the introductory part, polyelectrolyte brushes have attracted a great deal of interest because of its excellent lubrication behavior, antifouling behavior, 9) reversible adhesive-free adhesion, 10) etc.…”

“…The M w -dependence of the z-average, mean-square radius of gyration (hS 2 i z ) for the free PMAPS in a theta state in an aqueous NaCl solution at 0.074 M is given by 6) …”

“…11 as expressed by Eq. (6). In this experiment, we used the PILATUS detector (DECTRIS), a two-dimensional (2D) photon counting detector, with placing the grid mask resolution enhancer in front of the detection pixels for detecting the fluctuation of speckle intensity.…”