The self-assembling siloxane nanoparticles with three phases that increase tenacity of poly L-lactic acid (PLLA) were reported. The particles consist of a high-density siloxane phase (plural cores), an elastomeric silicone phase and a caprolactone oligomer (CLO) phase. The polymethyl-propyloxysiloxane (PMPS) was selected to form the elastomeric silicone phase with an appropriate (nanometer) size around the cores because it contains propyloxy groups, which have moderate polarity and reactivity at a low-molecular ratio in an adequate-length siloxane chain. Its use produces a loosely crosslinked siloxane network after the core formation. The caprolactone oligomer (CLO) was selected to form the outside phase because of its low polarity compared with those of isocyanate- propyltrimethoxysilane (IPTS) and PMPS, and its high affinity for the PLLA matrix. The amount of silicon originating from the IPTS and PMPS units was remarkably higher at several points around the center, which indicates that the nanoparticle had plural high-density siloxane cores formed mainly from the IPTS unit.
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