Molecular size and solubility conditions of polysilane macromolecules with different topology

Synthesis of bottlebrush polymers based on poly(N-sulfonyl aziridine) macromonomers

We synthesized bottlebrush polymers with polyaziridine brushes and a polynorbornene backbone by a grafting-through approach. The polyaziridine macromonomer aggregates in solution, but these aggregates disperse over the course of the polymerization.

Hyperbranched Silicone MDTQ Tack Promoters

Low molecular weight, highly crosslinked silicone resins are widely used as reinforcing agents for highly transparent elastomers and adhesion/tack promoters in gels. The resins are complex mixtures and their structure / property relationships are ill defined. We report the synthesis of a library of 2, 3 and 4-fold hyperbranched polymeric oils that are comprised of linear, lightly branched or highly branched dendronic structures. Rheological examination of the fluids and tack measurements of gels filled with 10, 25 or 50% dendronic oils were made. Viscosity of the hyperbranched oils themselves was related to molecular weight, but more significantly to branch density. The properties are driven by chain entanglement. When cured into a silicone gel, less densely branched materials were more effective in improving tack than either linear oils or Me₃SiO-rich, very highly branched oils of comparable molecular weight, because the latter oils underwent phase separation.

Polymer nanoparticle sizes from dynamic light scattering and size exclusion chromatography: the case study of polysilanes

Dynamic light scattering (DLS) and size exclusion chromatography (SEC) are among the most popular methods for determining polymer sizes in solution. Taking dendritic and network polysilanes as a group of least soluble polymer substances, we critically compare and discuss the difference between nanoparticle sizes, obtained by DLS and SEC. Polymer nanoparticles are typically in poor solution conditions below the theta point and are therefore in the globular conformation. The determination of particle sizes in the presence of attractive interactions is not a trivial task. The only possibility to measure, aggregation-free, the true molecular size of polymer nanoparticles in such a solution regime, is to perform the experiment with a dilute solution of globules (below the theta point and above the miscibility line). Based on the results of our polysilane measurements, we come to a conclusion that DLS provides more reliable results than SEC for dilute solutions of globules. General implications for the size measurements of polymer nanoparticles in solution are discussed.