- Title
- Influence of molecular weight on PNIPAM brush modified colloidal silica particles
- Creator
- Humphreys, Ben A.; Prescott, Stuart W.; Murdoch, Timothy J.; Nelson, Andrew; Gilbert, Elliot P.; Webber, Grant B.; Wanless, Erica J.
- Relation
- ARC.LE140100090 http://purl.org/au-research/grants/arc/LE140100090
- Relation
- Soft Matter Vol. 15, Issue 1, p. 55-64
- Publisher Link
- http://dx.doi.org/10.1039/c8sm01824c
- Publisher
- Royal Society of Chemistry
- Resource Type
- journal article
- Date
- 2019
- Description
- The effect of molecular weight and temperature on the phase transition and internal structure of poly(N-isopropylacrylamide) brush modified colloidal silica particles was investigated using dynamic light scattering (DLS) and small angle neutron scattering (SANS) between 15 and 45 °C. Dry particle analysis utilising transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) all confirmed the thickness of the polymer brush shell increased as a function of polymerisation time. Hydrodynamic diameter and electrophoretic mobility results revealed that the brush modified particles transitioned from swollen shells to a collapsed conformation between 15 and 35 °C. The dispersions were electrosterically stabilised over the entire temperature range investigated, with minimal thermal hysteresis recorded. Modelling of the hydrodynamic diameter enabled the calculation of a lower critical solution temperature (LCST) which increased as a function of brush thickness. The internal structure determined via SANS showed a swollen brush at low temperatures (18 and 25 °C) which decayed radially away from the substrate, while a collapsed block-like conformation with 60% polymer volume fraction was present at 40 °C. Radial phase separation was evident at intermediate temperatures (30 and 32.5 °C) with the lower molecular weight sample having a greater volume fraction of polymer in the dense inner region at these temperatures.
- Subject
- molecular weight; molecular temperature; poly(N-isopropylacrylamide) brush modified colloidal silica particles; dynamic light scattering; small angle neutron scattering; transmission electron microscopy; Fourier-transform infrared spectroscopy; thermogravimetric analysis
- Identifier
- http://hdl.handle.net/1959.13/1409585
- Identifier
- uon:36046
- Identifier
- ISSN:1744-683X
- Language
- eng
- Full Text
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