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Description:
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Nanoporous polymer hydrogels offer a desirable combination of mechanical ,
optical , and transport characteristics that have placed them at the core of a variety of
biomedical technologies including engineered tissue scaffolds , substrates for controlled
release of pharmaceutical compounds , and sieving matrices for electrophoretic
separation of DNA and proteins . Ultimately , we would like to obtain a detailed picture
of the nanoscale pore morphology and understand how it can be manipulated so that we
can rationally identify gel formulations best suited for a specific application . But this
goal has proven elusive because the most fundamental descriptors of the pore network
architecture (e .g . , the average pore size and its polydispersity ) are particularly difficult to
measure in polymer hydrogels .
Here we introduce an approach that enables both the mean pore size and the pore
size distribution to be quantitatively determined without prior knowledge of any physical
material parameters A novel technique to prepare TEM samples was developed so that
the nanoscale hydrogel pore size , pore shape and distribution are clearly visualized and quantitatively studied for the first time . The pore sizes of the hydrogel are also estimated
with rheology . A new fixture is used in the rheometer and the whole polymerization
process can be directly studied using an in -situ rheology experiment . A series of
thermoporometry experiments are also conducted , and suitable methods and equations to
study hydrogel pore size and distribution are chosen . The pore size derived from TEM ,
rheology , DSC is compared and their values are self -consistent . These techniques help
us understand how the nanoporous morphology of crosslinked polyacrylamide hydrogels
is influenced by their chemical composition and polymerization conditions .
It is interesting to find hydrogels with similar pore size but different distribution .
For two hydrogels with similar pore size , the broader the distribution , the faster the
release rate and the higher the accumulated release percentage . So we can control the
release of trapped molecules by simply varying the hydrogel pore size distribution . This
discovery would have a very promising potential in the application of pharmaceuticals . |