Effect of chain stiffness on the competition between crystallization and glass-formation in model colloidal polymers

TL;DR

This study investigates how chain stiffness influences the competition between crystallization and glass formation in model colloidal polymers, revealing how morphology varies with bending stiffness and cooling rate.

Contribution

It introduces a one-parameter model linking chain shape to bulk morphology, providing new insights into the packing and phase behavior of anisotropic colloidal polymers.

Findings

Flexible chains form close-packed crystallites with random-walk order.

Rodlike chains exhibit nematic ordering with close-packing.

Intermediate stiffness leads to glass formation and complex ordered phases.

Abstract

We map out the solid-state morphologies formed by model soft-pearl-necklace polymers as a function of bending stiffness $k_b$ spanning the range from fully flexible to rodlike chains. The ratio of Kuhn length to bead diameter ($l_K/r_0$) increases monotonically with increasing $k_b$ and yields a one-parameter model that relates chain shape to bulk morphology and yields insights into the packing of anisotropic particles. In the flexible limit, monomers occupy the sites of close-packed crystallites while chains retain random-walk-like order. In the rodlike limit, nematic chain ordering typical of lamellar precursors coexists with close-packing. At intermediate values of bending stiffness the competition between random-walk-like and nematic chain ordering produces glass-formation; the range of $k_b$ over which this occurs increases with the thermal cooling rate $|\dot{T}|$ implemented in our molecular dynamics simulations. Finally, values of $k_b$ between the glass-forming and rodlike ranges produce complex ordered phases such as close-packed spirals. Our results should prove useful for rational design of dense colloidal-polymer phases with desired morphologies.