Aleya Hasneen

Synthesis and characterization of low molecular weight poly(methyl acrylate)-b-polystyrene by a combination of ATRP and click coupling method

The combination of atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of well-defined block copolymers. Bromo terminated poly(methyl acrylate) (pMA-Br) was prepared by an ATRP initiator, ethyl-2-bromoisobutyrate (EBiB). Subsequently, the bromine chain end of pMA-Br was converted to an azide group by simple nucleophilic substitution reaction. α-Alkyn-ω-bromo-functionalized polystyrene was also synthesized by ATRP using the alkyn-functionalized initiator, propargyl-2-bromoisobutyrate (PgBiB). In both cases, the conversion was limited to a low level to ensure a high degree of chain end functionality. Then the coupling reaction between the azide end group in pMA-N3 and alkyn-functionalized PgBiB-pSt was performed by Cu(I)catalysis. This coupling reaction was monitored by gel permeation chromatography (GPC). The synthesized block copolymer was characterized by FT-IR,1H-NMR spectroscopy and1H-1H COSY correlation spectroscopy.

Synthesis and properties of polyurethane coatings: the effect of different types of soft segments and their ratios

Polyurethane (PU) coatings were prepared using siloxane polyol [poly(dimethyl siloxane), PDMS], polyether polyol [poly(propylene oxide glycol), PPG], and polyester polyol [poly(tetramethylene adipate glycol), PTAd]. The PTAd/PPG ratio was altered, whereas the PDMS content was fixed during PU synthesis. The structural elucidation of the synthesized PU was performed by Fourier transform infrared (FT-IR), 1H NMR, 13C NMR, and 29Si NMR spectroscopic techniques. The PU-film surface was characterized by X-ray Photoelectron Spectrometer and atomic force microscopy techniques and it was found that the surface smoothness depended on the PPG/PTAd ratio. The PU melting temperature, crystallinity, mechanical properties (tensile strength and Young’s modulus), and adhesive strength were also depended on the PPG/PTAd ratio. The adhesive strength to poly(vinyl chloride) of the coating with the proper polyol ratio (PTAd 12.50 mol% and PPG 16.67 mol%) was almost unaffected after immersion (three months) in artificial salt.

Properties of Waterborne Polyurethane Adhesives with Aliphatic and Aromatic Diisocyanates

A series of waterborne polyurethane (WBPU) adhesives were prepared with various ratios of aliphatic/aromatic diisocyanates, namely 4,4′-dicyclohexylmethane diisocyanate (H12MDI) as an aliphatic diisocyanate and 4,4′-diphenylmethane diisocyanate (MDI) as an aromatic diisocyanate with poly(tetramethyleneoxideglycol) (PTMG), ethylene diamine (EDA) and dimethylol propionic acid (DMPA). 1H-NMR spectroscopy was utilized to investigate the side reaction at the dispersion step during synthesis of WBPU dispersions with respect to aliphatic, aromatic and mixed diisocyanates. The tensile strength, Youngs modulus, elongation at break (%), storage modulus, glass transition temperature and adhesive strength were measured with respect to aliphatic/aromatic diisocyanate contents. The adhesive strength was maximum using mixed diisocyanates containing 25 mol% MDI in WBPU adhesives.

Properties of Waterborne Polyurethane/CNT Nanocomposite Adhesives: Effect of Countercations

Two series of waterborne polyurethane (WBPU)/carbon nanotube (CNT) nanocomposites were prepared with various CNT contents (0–1.50 wt%). We used a metal-hydroxide (copper hydroxide, Cu(OH)2) and amine (triethylamine, TEA) as the countercation in the nanocomposites. The interaction of the countercations with the CNTs in the nanocomposite was characterized by TEM, and the interaction effects on the properties, such as the glass transition temperature (Tg), storage modulus, tensile strength, Youngs modulus and adhesive strength, were investigated. The CNTs were homogeneously (optimum) dispersed at concentrations of up to 1.25 and 1.00 wt% for the metal-hydroxide and amine series, respectively. At the optimum CNT content, the tensile strength and adhesive strength were maximized in each series. However, the adhesive strength of the WBPU/CNT nanocomposite with the metal-hydroxide countercation was less affected than with the amine-countercation after immersing the adhesive bonded nylon fabrics in water (for up to 48 h).

Properties of Waterborne Polyurethane/Clay Nanocomposite Adhesives with Various Countercations of Carboxyl Acid Salt Group

Four series of waterborne polyurethane (WBPU)/clay nanocomposite adhesives were prepared using three different countercations, namely triethylamine (TEA), lithium hydroxide (LiOH) and copper hydroxide (Cu(OH)2 ) as well as one mixed countercation of TEA and Cu(OH)2 (1:0.5). The interaction of carboxyl acid salt group using different countercations with clay platelet was characterized by SEM and TEM, and the interaction effects on properties such as water swelling (%), thermal stability, tensile strength, glass transition temperature ( T g ), and adhesive strength were investigated. The tensile strength, water resistance and adhesive strength increased with increasing clay content up to an optimal value at which point the maximum tensile strength, water resistance and adhesive strength were recorded for each series. However, the optimal clay contents were 1.00 and 0.50 wt% for TEA/LiOH mixed countercation series and (Cu(OH)2 ) series, respectively. Among all of the samples the maximum tensile strength, water resistance and adhesive strength were found using mixed countercation (TEA and Cu(OH)2 = 1:0.5) with 1 wt% clay content.

Biological Synthesis of Alkyne-terminated Telechelic Recombinant Protein

In this study, we demonstrate that the biological unnatural amino acid incorporation method can be utilizedin vivo to synthesize an alkyne-terminated telechelic protein. Synthesis of terminally-functionalized polymers such as telechelic polymers is recognized to be important, since they can be employed usefully in many areas of biology and material science, such as drug delivery, colloidal dispersion, surface modification, and formation of polymer network. The introduction of alkyne groups into polymeric material is particularly interesting since the alkyne group can be a linker to combine other materials using click chemistry. To synthesize the telechelic recombinant protein, we attempted to incorporate the L-homopropargylglycine into the recombinant GroES fragment by expressing the recombinant gene encoding Met at the codons for both N- and C-terminals of the protein in the Met auxotrophicE. coli via Hpg supplementation. The Hpg incorporation rate was investigated and the incorporation was confirmed by MALDI-TOF analysis of the telechelic recombinant protein.