Soft Matter Physics

 

1. Irreversible adsorption of flexible polymers

 

Polymer adsorption is a fundamental process in polymer science. A large number of theoretical works have addressed equilibrium properties. Many experiments however suggest a picture where relaxation times are very large and non-equilibrium polymer layers are the rule rather than the exception. Motivated by a lack of theoretical understanding of non-equilibrium layers, we developed theory describing the structure and formation kinetics of layers which result from irreversible polymer adsorption onto surfaces and compared theory to experiment. A review on theoretical and experimental work on non-equilibrium polymer adsorption was published in J. Phys.: Cond. Matter.

References

O’Shaughnessy and Vavylonis, J. PHYS.: CONDENS. MATTER 17, R63–R99 (2005).

O’Shaughnessy and Vavylonis, EUROPHYS. LETT. 63, 895–901 (2003).

O’Shaughnessy and Vavylonis, EUR. PHYS. J. E 11, 213–230 (2003).

O’Shaughnessy and Vavylonis, PHYS. REV. LETT. 90, 056103 (2003).

 

 

2. Kinetics of synthetic polymerizations.

 

Living polymer dynamics.  Living polymerizations is a broad class of reversible polymerizations which includes biopolymers (actin, microtubules) and synthetic polymers such as alpha-methylstyrene. We focused on the dynamics of synthetic polymers as model systems for understanding basic properties common to all living polymers. Very little was known about dynamics, despite many equilibrium studies. The main theoretical result was that the response of the polymer length distribution to a perturbation is ultrasensitive, i.e. highly dynamically susceptible to small perturbations.

References

O’Shaughnessy and Vavylonis, EUR. PHYS. J. E 12, 481–496 (2003).

O’Shaughnessy and Vavylonis, PHYS. REV. LETT. 90, 118301 (2003).

 

Pulsed laser polymerization (PLP). Analytical solutions were obtained for the polymer length distribution in PLP, the most successful method for measuring polymerization rate constants in free radical polymerization.

 

References

O’Shaughnessy and Vavylonis, MACROMOL. THEORY SIMUL. 12, 401–412 (2003).

 

 

3. Reaction-diffusion systems.

 

First principles theory.  Theory was developed describing the kinetics of A-B reactions between particles which can react only in a thin stationary interfacial region separating A and B bulks. Very little had been established about fixed interface reaction kinetics, in contrast to extensively studied bulk kinetics (“A + B -> 0”). Extending this approach, the effects of finite reactivity in bulk reactions were also examined.

References

O’Shaughnessy and Vavylonis, PHYS. REV. LETT. 84, 3193–3196 (2000).

O’Shaughnessy and Vavylonis, EUR. PHYS. J. E 1, 159–177 (2000).

O’Shaughnessy and Vavylonis, EUROPHYS. LETT. 45, 653–658 (1999).

 

Polymer-polymer reactions kinetics in bulk and at interfaces. The general theory of interfacial reaction kinetics was applied to reaction kinetics at immiscible polymer interfaces and in bulk polymer reactions. Understanding such kinetics is important in polymer reactive blending commercial applications where the reactively formed diblock copolymers reinforce the interface and enhance mixing.

 

References

O’Shaughnessy and Vavylonis, MACROMOLECULES 32, 1785–1796 (1999).

O’Shaughnessy and Vavylonis, EUROPHYS. LETT. 45, 638–644 (1999).

O’Shaughnessy and Vavylonis, EUR. PHYS. J. B 6, 363–372 (1998).