Large-scale microsegregation in polyacrylamide gels (spinodal gels)

Asnaghi, D.; Giglio, M.; Bossi, Alessandra Maria; Righetti, P. G.

doi:10.1063/1.468792

Cited by 46 publications

(42 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore the above scenario for gelation does not apply to our system. As mentioned in the Introduction gelation can also result from a fluid-fluid phase separation which is arrested at some intermediate stage either by a sol-gel transition [13,27] or by a glass transition [14,15] leaving the system in a state of microphase separation. A thermodynamic model for this mode of gelation was presented by Frank and Keller [28] and a kinetic model by Sciortino et al [29].…”

Section: Discussionmentioning

confidence: 99%

Transient gelation by spinodal decomposition in colloid-polymer mixtures

Verhaegh

Asnaghi

Lekkerkerker

et al. 1997

Physica A: Statistical Mechanics and its Applications

146

154

View full text Add to dashboard Cite

We have investigated with small angle light scattering and optical microscopy transient gelation phenomena which occur in phase-separating colloid-polymer mixtures. The scattering intensity distribution shows a peak at non-zero wave vector and satisfies the asymptotic q-4 Porod behaviour. Consistent with these observations, optical micrographs show an alternating pattern of dark and bright domains. These findings suggest that the polymer-induced depletion forces lead to the formation of a bicontinuous network of colloid-rich and colloid-poor domains, via a spinodal decomposition process. This bicontinuous network rapidly attains a gellike character as indicated by the arrest of speckle fluctuations. The occurrence of the gel is ascribed to polymer-induced aggregation between the colloids in the colloid-rich phase. Due to the reversible nature of the aggregation the network restructures and eventually the gel collapses, as is manifested by the rapid separation of the colloid-rich phase from the colloid-poor phase.

show abstract

Section: Discussionmentioning

confidence: 99%

Transient gelation by spinodal decomposition in colloid-polymer mixtures

Verhaegh

Asnaghi

Lekkerkerker

et al. 1997

Physica A: Statistical Mechanics and its Applications

146

154

View full text Add to dashboard Cite

show abstract

“…0.0012 nm À1 . This q À3 behavior observed in the MC solution suggests that the fractal dimension of the boundary surface of the pores in this gel is equal to 3 and has been observed in highly porous materials, such as lignite coals, [39] polymer gelations [35] and colloidal solutions. [40] To determine the kinetics of the phase-separation process, we constructed a semilogarithmic plot of scattering intensity versus time (s) at different q values, shown in Figure 4 for 5 g Á L À1 MC in the presence of 5% (w/w) NaCl after a temperature jump from 0 8C to 49 8C and isothermal annealing at 49 8C.…”

Section: Resultsmentioning

confidence: 95%

“…Similar results were obtained for the samples quenched to 48, 50 and 51 8C (not shown here). Asnagi et al [35] used the SALS technique to study the gelation process in polyacrylamide solutions in the presence of polyethylene glycol (PEG). They observed that the phase separation occurs via SD, and two maxima were observed for some analyzed compositions with lower PEG concentrations.…”

Section: Resultsmentioning

confidence: 99%

Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

Villetti

Soldi

Rochas

et al. 2011

Macro Chemistry & Physics

View full text Add to dashboard Cite

Phase‐separation dynamics are investigated by SALS in aqueous MC solutions in the presence of 5% NaCl, promoted by a quench temperature. The observed scattering peak indicates that the phase separation occurs by the SD mechanism, leading to a bicontinuous structure. A semilog plot of I(q) against time in the early stage of SD gives a straight line, but the position of qmax varies; also, a Cahn–Hilliard plot indicates that diffusive processes dominate and the data can be described by linear CHC theory. Dapp shows a kinetic dependency on the quench temperature. The spinodal temperature of the sample is 41 °C. In the late stages, S(q,t) collapses into a universally time‐independent curve. magnified image

show abstract

“…Among the reasons for the formation of structural heterogeneities in the growing networks, the spontaneous tendency of monomers, cross-linkers and solvent to separate during the polymerisation into uniform clusters in different spatial regions is a major factor (Kloosterboer, 1998;Anseth et al, 1996). Such segregation is defined as spinodal decomposition (Asnaghi et al, 1995), it generates local environments composed of molecules with 0956-5663/$ -see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2010.02.015 similar properties (hydrophobicity and density) and ultimately results in different microgelation environments in the same polymerisation reaction and thereby gives rise to heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of controlled polymeric cross-linked coatings via iniferter polymerisation in the presence of tetraethyl thiuram disulphide chain terminator

Bossi

Whitcombe

Uludag

et al. 2010

Biosensors and Bioelectronics

Self Cite

View full text Add to dashboard Cite

A "grafting from" approach has been used for controlled deposition of cross-linked polymers by living radical polymerisation. Borosilicate glass was modified with N,N-diethylaminodithiocarbamoylpropyl(trimethoxy)silane, in order to confine the iniferter reactive groups solely at its surface, then placed in solution with monomers and cross-linker. The polymerisation was initiated by UV irradiation. Formation of the cross-linked polymers was studied in terms of time course of the reaction, type of monomers incorporated and influence of oxygen. Grafted surfaces were characterised by AFM, FT-IR, ellipsometry and contact angle measurements. The ability to control the grafted layer improved dramatically when the chain terminator agent, N,N-N',N'-tetraethyl thiuram disulphide (TED) was added. Upon irradiation TED increases the concentration of passive capping radicals and decreases the possibility of recombination of active macro-radicals, thus prolonging their lifetime. In the absence of TED the thickness of produced coatings was below 10 nm. TED added at different concentrations assisted in the formation of grafted layers of 10-130 nm thickness. Iniferter chemistry in the presence of TED can be used for growing nanometre-scale polymer layers on solid supports. It constitutes a robust general platform for controlled grafting and offer a general solution to address the needs of surface derivatisation in sensors technology.

show abstract

Large-scale microsegregation in polyacrylamide gels (spinodal gels)

Cited by 46 publications

References 27 publications

Transient gelation by spinodal decomposition in colloid-polymer mixtures

Transient gelation by spinodal decomposition in colloid-polymer mixtures

Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

Synthesis of controlled polymeric cross-linked coatings via iniferter polymerisation in the presence of tetraethyl thiuram disulphide chain terminator

Contact Info

Product

Resources

About