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Trail of pore shape and temperature-sensitivity of poly(N-isopropylacrylamide) hydrogels before and after removing Brij-58 template and pore formation mechanism
Trail of pore shape and temperature-sensitivity of poly(N-isopropylacrylamide) hydrogels before and after removing Brij-58 template and pore formation mechanism
To investigate the change upon structure and temperature-sensitivity of
porous hydrogel before and after removing template and confirm the pore
formation mechanism, a series of hydrogels (abbreviated as CLH) based on N-isopropylacrylamide (NIPAM) serving as
functional monomer and polyoxyethylene-20-cetyl-ether (Brij-58) acting as template
were obtained. The chemical composition, crystal structure and temperature-sensitivity
of PNIPAM hydrogels before and after template were compared and confirmed by
FTIR, XRD and DSC. The optical performance, pore shape and (de)swelling
behavior of prepared CLH hydrogels were investigated by UV/vis, SEM and gravimetric method.
The disappearance of characteristic absorption peak at 1062-1146 cm?1 and coincidental
absorption peak at 195nm, and recovery of diffraction peak at 2θ = 7.8° and 2θ
= 20.75° all confirmed that Brij-58 plays a template
action and could be removed after 48h. With increasing mass ratios of Brij-58/NIPAM
from 0 to 2, the critical time of optical transmittance of CLH hydrogels
dropping to 0 from 100 decreases to 7.5 min from 22 min, while maximum equilibrium swelling ratios increase from
6.3 to10.31g/g. SEM
graphs show that, with increasing mass
ratios of Brij-58/NIPAM from 0 to 2, CLH hydrogels firstly form homogeneous
and smaller pore, and then pore sizes increase from 4-10μm to 50-100μm together
with interconnected porestructure.
With increasing mass ratios of Brij-58/NIPAM,
thermo-responsibility of CLH hydrogels containing Brij-58 template disappeared
gradually and then recovered after removing template. The deswelling rates of CLH hydrogels depend
on the mass ratios of Brij-58/NIPAM,
as r=Brij-58/NIPAM≤1/10, the hydrogels lose over 70% water within 60min,
while the hydrogel loses over 70% water within 10min as r=Brij-58/NIPAM=2. This
kind of templated hydrogel with adjustable porous structure has much potential
in the fields of drug delivery system, tissue engineering and chemical
separation.
