Stearyl Methacrylate-Based Polymers as Crystal Habit Modifiers for Triacylglycerols

Abstract

Triacylglycerides (TAGs) are ubiquitous and naturally-occurring fat molecules that can make materials with diverse textural, mechanical and optical properties. These properties are intimately linked to their complex hierarchical crystal structures, which can be controlled by additives that interfere with crystallization. A series of semi-crystalline bottlebrush-like copolymers has been developed to modify TAG crystallization and influence crystal habit. Synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, these copolymer additives combine crystalline poly(stearyl methacrylate) with amorphous poly(oleyl methacrylate) in either block or statistical architecture. Upon cooling mixtures of these copolymers with solutions of tristearin (SSS) in triolein (OOO), the polymeric additives affected SSS crystallization at multiple length-scales. Microscopy analysis revealed control over SSS crystal morphology indicative of crystal aggregation, whilst small and wide angle x-ray diffraction (SAXD/WAXD) offered insight into the underlying mechanism of action. Analysing the physical broadening of lamellar peaks suggested that the fraction of amorphous poly(oleyl methacrylate) controls the thickness of primary nanoplatelets, and crystal structures derived from WAXD showed that the less stable or '-polymorphs of SSS are stabilized by block or statistical copolymers, respectively. Exploiting these additives to simultaneously manipulate the packing of TAG molecules within lamellae, the size of primary crystallites, and the aggregation of crystallites could diversify fat material properties and supplement wide-ranging applications.

Liquid Lipids Act as Polymorphic Modifiers of Tristearin-Based Formulations Produced by Melting Technologies

“…Recently, the addition of polymeric additives (synthetic homopolymers of stearyl methacrylate and oleyl methacrylate) has been shown to impact the crystallization and the crystal habit of tristearin. Depending on the polymer characteristics, the effect resulted either in the stabilization of the metastable (α- or β′) polymorphs or in the modification of the crystals size and morphology [ 29 ]. In all the reported studies, however, the purpose of the additives consisted mostly in the stabilization of metastable polymorphs.…”

Multiple Routes to Bicontinuous Cubic Liquid Crystal Phases Discovered by High-Throughput Self-Assembly Screening of Multi-Tail Lipidoids

“…Specifically, lipidoids with the longest tails (16) showed one sharp peak at q ~ 15 nm -1 at 25°C (e.g. Figure S3K), corresponding to a hexagonal alkyl chain packing, also seen in triacylglycerols 42 and lipids with small headgroups in the gel phase. 43 Upon heating, this high q peak disappeared, and in many cases the remaining peaks in the SAXS region were equally spaced, indicative of a lamellar LC.…”

Multiple Routes to Bicontinuous Cubic Liquid Crystal Phases Discovered by High-Throughput Self-Assembly Screening of Multi-Tail Lipidoids

“…Specifically, lipidoids with the longest tails (16) showed one sharp peak at q ~ 15 nm -1 at 25°C (e.g. Figure S3J), corresponding to a hexagonal alkyl chain packing, also seen in triacylglycerols [42] and lipids with small headgroups in the gel phase. [43] Upon heating, this high q peak disappeared, and in many cases the remaining peaks in the SAXS region were equally spaced, indicative of a lamellar LC.…”