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Abstract
In the present study, the synthesis of poly(1,1-dimethylsilacyclobutane) (PDMSB) by anionic ring opening polymerization (ROP) is reinvestigated, leading to narrowly distributed molar masses (polydispersities 1.04–1.15) in the range of 2.3 to 60 kg mol−1. Investigations of thermal behavior for low molar mass PDMSB revealed an untypical multiple peaks melting phenomenon, which at first glance, seems to be of the same origin as low molar mass poly(ethylene oxide)s. Small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) measurements are done, proving the fast crystallization and subsequent recrystallization for investigated low molar mass samples. Synthetic attempts are expanded to the surface-initiated anionic ROP of 1,1-dimethylsilacyclobutane (DMSB) monomer from the surface of cross-linked polystyrene (PS) nanoparticles. Novel polycarbosilanes (PCS)/organic core/shell particles are obtained, which are investigated by using transmission electron microscopy (TEM) and dynamic light scattering (DLS) experiments. First insights into the crystallization behavior of surface-attached PDMSB chains reveal that crystallization seems to be hindered.
Highlights
Polycarbosilanes (PCS) gained considerable attention in the last two decades, due to their interesting optoelectronic and heat-resistant applications, but most important are applications as oxygen-free ceramic precursors [1,2,3,4,5]
After a longer reaction time (>1 h) under applied conditions, PDMSB samples showed a significant shoulder in SEC traces shifted to higher molar masses, which can be assumed to be caused by an undesired coupling process of living chain ends with the silane moieties
(PDMSB) homopolymers with molar masses ranging from 2.3 kg mol−1 to 60 kg mol−1 with low polydispersities for every sample (PDI between 1.04 and 1.15) was reported
Summary
Polycarbosilanes (PCS) gained considerable attention in the last two decades, due to their interesting optoelectronic and heat-resistant applications, but most important are applications as oxygen-free ceramic precursors [1,2,3,4,5]. Strategies range from Kumada rearrangement of silanes [10], Grignard coupling [11,12,13] to Pt(0)-catalyzed ring opening polymerization (ROP) of cyclic carbosilanes [9,14] The latter method has the advantage that well-defined hyperbranched materials can be obtained with high ceramic yields after pyrolysis. The synthetic protocol for surface-initiated anionic ROP of DMSB leads to novel well-defined PCS/organic core/shell structures, which are promising candidates to gain materials for SiC-based ceramic particles or hollow spheres after pyrolysis. Such SiC materials find important applications for electric devices, such as sensors or in catalysis [38,39,40]
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