Polymerization of conducting polymers confined to free surfaces: a comparison of the Langmuir-Blodgett polymerizations of 3-alkyl pyrroles and 2-alkyl anilines

Duran, Randolph S.; Zhou, Huanchun

doi:10.1016/0032-3861(92)90599-r

Cited by 23 publications

(8 citation statements)

References 11 publications

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“…If the contraction is severe enough, cracks can form, preventing the formation of a continuous film. Polymerization at constant surface pressure ensures that the retraction of the film does not fracture the network and also provides an alternative means to monitor the progression of the reaction, through observation of changes in the area. − Unfortunately, for some applications it is impossible to maintain constant surface pressure (e.g., liposomes, planar supported bilayers). Instead, the molecules are held at constant density, and experimental data taken under constant pressure conditions in a Langmuir trough may not be directly transferable to these systems.…”

Section: Kinetic Modelmentioning

confidence: 99%

Surface Shear Rheology of a Polymerizable Lipopolymer Monolayer

et al. 2002

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We have used an interfacial stress rheometer to study the changes in the mechanical shear properties of a Langmuir monolayer of a linear polymer with reactive side chains. The polymer investigated had a linear hydrophilic backbone consisting of poly(ethylene imine-co-ethyl oxazoline) and contained 20% hydrophobic sorbyl side chains, making it amphiphilic and capable of forming stable monolayers at the air-water interface. The sorbyl moiety in the side chain was photopolymerizable at 254 nm. Upon exposure of the film to UV light, the surface dynamic shear modulus, Gs′, which is a measure of the elasticity, increased 1000-fold to ∼2 mN/m. This large increase in elasticity arises from the formation of a network by reaction of side chains on different polymer backbones. Rubber-like properties were deduced from the frequency dependence of the moduli and from creep experiments, where elastic recoil could be observed upon removing the applied stress. Such a network could be formed over a wide range of surface pressures ranging from 5 to 25 mN/m. We investigated the cross-linking kinetics upon UV exposure as a function of temperature, initial surface pressure, and light intensity. We have developed a lumped kinetic model that agrees with the transient behavior of the storage modulus, our measure of the density of cross-link points. The reaction was independent of temperature (over 10-30 °C) and exhibited a first-order dependence on light intensity. Since the reactive side groups must be in close enough proximity for the interpolymer side chain reaction to occur, a threshold side chain density is required to form junction points. After extensive UV exposure, the elasticity of the network degraded, and the rate of degradation was faster for films polymerized at lower initial surface pressures.

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Section: Kinetic Modelmentioning

confidence: 99%

Surface Shear Rheology of a Polymerizable Lipopolymer Monolayer

et al. 2002

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“…Early work done in our group noted that the Langmuir film polymerization rate of 2-pentadecylaniline ( 3a ) was dependent on the applied surface pressure. , In this study, the polymerization of 3a at the air−aqueous interface was done in the presence of the strong chemical oxidant, ammonium peroxydisulfate, and an acid . The polymerization was monitored by observing the barrier movement needed to maintain a specific applied surface pressure.…”

Section: Introductionmentioning

confidence: 97%

“…The polymerization was monitored by observing the barrier movement needed to maintain a specific applied surface pressure. The area change per molecule was attributed to the replacement of van der Waals radii by covalent bonds between monomer molecules and conformational differences between monomer and polymer. , At higher applied surface pressures, the polymerization rate was faster than that at lower pressures, suggesting that the reactive group conformation at the interface might have a significant effect on the polymerization rate at an interface.…”

Section: Introductionmentioning

confidence: 99%

“…The R p of 3a at the air−aqueous interface was determined and a single rate constant assigned. , However, this constant was assigned from the point of a maximum reaction rate, normally 10−30 min into the polymerization. While showing the effect of surface pressure on reaction rate, these studies did not address the autoacceleration rate effect on the complex polymerization kinetics.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Polymerization and Surface Behavior of Alkyl-Substituted Aniline Surfactants at the Air−Aqueous Interface: A Kinetic Study

Kloeppner

Duran

1998

Langmuir

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The surface behavior of 2-, 3-, and 4-pentadecylaniline (3a, 3b, and 3c, respectively) was studied at the air−aqueous interface of an acidic subphase. Surface dipole moments (μn) were calculated from the surface potentials (ΔV) of 3a−c and were related to the orientation of the anilinium ion at the interface. Further, 3a and 3b were polymerized in a Langmuir film, and analysis of the absorption spectra showed that the resulting polymers were in different oxidative states upon completion of the polymerization. A method that monitors the change in the mean molecular area (A) of the surfactant at a constant applied surface pressure and predicts the concentrations of monomer and polymer and/or oligomer at the interface in order to determine the formation rate (R p) of poly(alkylaniline) is presented. The R p values of 3a and 3b are expressed in terms of the concentrations of the monomer and polymer at the interface. It was determined that the R p of 3a was dependent on the applied surface pressure while 3b showed little dependence on surface pressure. Differences in R p can be explained by the conformation of the anilinium group and the steric hindrance of the alkyl group at the interface. A characteristic “autoacceleration effect” was observed for both 3a and 3b but was more significant in the case of 3a.

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“…[20][21][22][23][24] Some ortho-substituted anilines have also been polymerized at an air-water interface using the Langmuir-Blodgett (LB) technique. [25][26][27][28] In this technique a reaction occurs under anisotropic conditions caused by the surfaceinduced orientation of the monomer, and the polymer chains in the resulting monolayer may have enhanced longrange configurational, orientational, and positional ordering and greater anisotropic properties than polymers synthesized by conventional methods.…”

Section: Introductionmentioning

confidence: 99%