Visualisation and characterisation of heterogeneous bimodal PDMS networks

• Published in: RSC advances Vol. 4; no. 14; pp. 6939 - 6945
• Main Authors: Madsen, F. B., Daugaard, A. E., Fleury, C., Hvilsted, S., Skov, A. L.
• Format: Journal Article
• Language: English
• Published: 2014
• Subjects: Compatibility
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C3RA47522K

The existence of short-chain domains in heterogeneous bimodal PDMS networks has been confirmed visually, for the first time, through confocal fluorescence microscopy. The networks were prepared using a controlled reaction scheme where short PDMS chains were reacted below the gelation point into hyperbranched structures using a fluorescent silicone compatible cross-linker. The formation of the hyperbranched structures was confirmed by FTIR, super(1)H-NMR and size exclusion chromatography (SEC). The short-chain hyperbranched structures were thereafter mixed with long-chain hyperbranched structures to form bimodal networks with short-chain domains within a long-chain network. The average sizes of the short-chain domains were found to vary from 2.1 to 5.7 mu m depending on the short-chain content. The visualised network structure could be correlated thereafter to the elastic properties, which were determined by rheology. All heterogeneous bimodal networks displayed significantly lower moduli than mono-modal PDMS elastomers prepared from the long polymer chains. Low-loss moduli as well as low-sol fractions indicate that low-elastic moduli can be obtained without compromising the network's structure.