Abstract of the Thesis Polymers for Novel Applications: I. Hydrogel Implants for Post-Lumpectomy Patients and II. Cellulose Nanofibrous Composite Membrane for Heavy Metal Adsorption by Si Hui Guan Master of Science in Chemistry Stony Brook University 2012 I. Breast cancer patients who have followed the lumpectomy procedure to take out the infected tissue will leave an empty space in their breasts. The aim of this study is to design and synthesize a novel Pluronics-based hydrogel that is radiation resistant, osmotic pressure balanced, radiological imaging friendly, while temporarily replicating the physical and mechanical properties of the native breast tissue. In order to produce a photo-cross-linkable hydrogel, Pluronics F127 was chemically modified from copolymer Poloxamer 407, by using diacrylates. The modified hydrogel, to our knowledge, is non-toxic and biocompatible to the human body. Furthermore, it can act as a scaffold to regenerate natural tissue in the presence of growth factors. In the process, the hydrogel will be designed to degrade slowly in order to accommodate the regenerated tissue as well as to maintain the shape of the breast. Therefore, this new hydrogel will be an innovative approach for breast reconstruction applications. II. The heavy metal pollution problem is an environmental concern in developing and developed countries. The current study is designed for a novel microfiltration membrane consisting of cellulose nanofibers (CNF) and amino-modified cellulose nanofibers (mCNF), infused in an electrospun polyacrylonitrile (PAN) scaffold on a non-woven polyethylene terephthalate (PET) support, which can effectively remove a range of heavy metals from water. The high porosity, large surface area per unit volume and dense charges of the nanoscale-web structure can provide the resultant micro-filtration membrane with an ability to remove 159mg Pb (II) per gram CNF (0.766 mmol/g) and 71mg Cr (VI) per gram mCNF(1.36 mmol/g) by static adsorption. For dynamic adsorption, the CNF composite membrane is able to remove 259 mg/g (1.25 mmol/g) Pb (II), while the mCNF composite membrane is able to remove 100 mg/g (1.92 mmol/g) Cr (VI). Furthermore, the composite membrane can be recycled by utilizing a desorption cycle, which can remove 100 % of the adsorbed metal ions from the membrane. Therefore, a low cost, safe and effective pathway for heavy metal ion removal has been developed.