The hydrogen\|bond defect of water in aqueous solution of a well\|defined poly(2\|hydroxyethyl acrylate)(PHEA) with different molecular weights and concentrations was studied by Raman spectrum analysis. The pre\|designed molecular weight of PHEAs with narrow polydispersities (<1 20) were synthesized via atom transfer radical polymerization (ATRP). It was found that in a low concentration PHEA aqueous solution(5?wt%), with the increase of molecular weight, the hydrogen bond defect increased markedly, but in a high concentration solution (25?wt%), the hydrogen bond defect was not sensitively affected by the molecular weight of PHEA. At higher temperature, the N value decreased due to the destroying of the hydrogen bond formation between water and the hydrophilic polymer chain in aqueous solutions.
The hydrogen\|bond defect of water in PVA hydrogels was studied by Raman spectral analysis. The PVA hydrogels were prepared from PVA of different DP in different concentrations via freeze/thawed method.It was found that the hydrogen bond defect of water in PVA hydrogels is affected by their crystallinity which was depended on the molecular weight and concentration of PVA and also the number of freeze/thawed cycles.After swelling in water for 24?h,partial VA units were released from the crystalline regions,this means that more `free’ VA units could bond with water in PVA hydrogels,causing the decrease of C value and the increase of N value.
A Raman spectroscopic study on the hydrogen\|bond defect of water in 2\|hydroxyethyl (meth)acrylate hydrogels crosslinked by ethylene glycol dimethacrylate (EGDMA) and polyethylene glycol dimethacrylates were undertaken.It was found that PEGDMA 16 possessed a different behavior on the hydrogen\|bond defect from EGDMA and PEGDMA 9.That is,the extents of hydrogen\|bond defect for EGDMA and PEGDMA 9 decreased with the increase of crosslinking density,whereas for PEGDMA 16,as the crosslinking density is bigger than a certain value,the hydrogenbond defect is increased with the increase of crosslinking density.This is caused by the weaker effect of —CH 2OCH 2— in the PEGDMA 16 to the hydrogen\|bond defect of water than that of —OH in HEA and HEMA.
