In this work, a series of shape memory biopolymers based on a dual-phase poly(lactic acid) and poly(hydroxybutyrate)rubber copolymer (PLA/PHB-rubber) were developed, exhibiting significant flexibility and well-balanced shape memory (SM) performance. The incorporation of PHB-rubber emerged as numerous well-dispersed microsized domains that partially penetrated the PLA domain, as revealed by the reduction of glass-transition temperature in the differential scanning calorimetry (DSC). The overall increase in crystallinity with the increasing PHB-rubber contributed to a high shape fixity of ∼99% and recovery of ∼95%, where the crystalline domains of PLA and PHB regions constituted as effective anchors for shape fixing, while the rubbery segment that constituted the switching phase provides considerable chain crusade. Concurrently, the PHB-rubber phase promotes considerable interfacial interaction with the PLA phase, as revealed by the field-emission scanning electron microscopy (FESEM) studies. Remarkably, the macroscopic triple-coiled shape recovery was accomplished in just 3 s. The developed dual-phase binary polymer shows great potential as a shape memory polymer for biomedical applications.

This study considers the consequences of adding grains to an air−liquid interface from a funnel. Depending on the grain contact angle and liquid surface tension, the interface is found to support a single or multiple layers of grains, forming a granular stack. By continuing to add grains, the stacks grow until either the lower grains disperse in the liquid, or the complete stack breaks free from the surface and sinks as a dry powder lump. Herein, the effects of grain contact angle, density, and size on these processes are studied experimentally, and a theoretical analysis is given. The maximum number of grains contained in a floating stack and its critical depth are observed to increase as the grain size decreases. The maximum number of grains scales with the bond number (Bo) as Bo −1.82 when stack detachment is observed and with an exponent −2.0 when grains disperse into the liquid. As a result of these different scaling exponents, a critical bond number above which grains wet and disperse can be identified. Favorable conditions for dispersion are achieved with larger grains and, to a lesser extent, by lower surface tension and contact angle. The critical bond number separating grain dispersion from lump formation increases with an increasing grain contact angle, thus providing a physical justification for increasing grain size with common processes such as granulation or agglomeration. Conversely, a quantitative framework to interpret the limitations in dispersing small grains is proposed, justifying the need for low contact angle or liquids with low surface tensions, both favored by the use of surfactants. The present findings have identified conditions under which lump formation occurs, and hence how these undesired phenomena can be avoided in applications requiring the efficient dispersion of grains across a liquid interface.

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