Synthesis Of The Hyperbranched Polymers And Their Application In Functional Modification Of Cotton

Cotton, a most important natural textile, is widely used in clothing fields for its excellent properties such as regeneration, bio-degradation, softness, affinity to skin, and hygroscopic property. However, when dyeing cotton fabric with reactive dyes, large quantities of salt (30-150 g/l) are needed to overcome the static repulsion between cotton fibers and reactive dyes in order to promote dyeability and simultaneously result in heavy environmental pollution. In addition, cotton fabric is susceptible to micro-organisms, such as bacteria and fungi. When multiplying in cotton fabric, micro-organisms not only cause physicochemical degradation such as discoloration, mechanical strength loss, and foul odor generation, but also may adversely affect human health. The purpose of the present work is to synthesize a water-soluble amino-terminated hyperbranched polymer (HBP-NH2) and 2-Hydroxypropyltrimethylammonium chloride hyperbranched polymer (HBP-HTC). Then apply the HBP-NH2 and HBP-HTC to fuctional modification of cotton fabric to improve its dyeability and provide it with antimicrobial properties.The HBP-NH2 was synthesized from methyl acrylate and diethylene triamine by polycondensation. Then the HBP-HTC was synthesized from HBP-NH2 and 2, 3-Epoxypropyltrimethylammonium chloride (GTMAC) as a grafting agent in aqueous solution. Their molecular weights and possible structure were characterized by Gel permeation chromatography (GPC), Fourier transform infrared spectrophotometry (FTIR) and Nuclear magnetic resonance spectroscopic (1H-NMR) respectively. Dissolution characteristic, thermal performance and UV absorbing capability of the HBP-NH2 and HBP-HTC were also studied for their application in textile fields.In order to improve the dyeability of the cotton fabric with reactive dyes, the cotton fabric was pretreated with HBP-NH2 aqueous solution directly. The dyed HBP-NH2 pretreated cotton fabric (HCF) exhibited similar K/S value even in the absence of electrolyte when dyed with some reactive dyes. The washing fastness, rubbing fastness and levelling properties of the dyed HCF in salt-free dyeing were also good in comparison to the dyed CF in conventional dyeing. To further improve the dyeability of the cotton fabric and achieve salt-free dyeing with reactive dyes, the oxidized cotton farbics were obtained firstly by selective oxidation of cotton fabric with sodium periodate aqueous solution. Subsequently, the HBP-NH2 grafted oxidized cotton fabric (HGCF) was prepared by the reaction between the oxidized cotton fabric and the HBP-NH2 as a grafting agent in aqueous solution. Fourier transform infrared spectrophotometry (FTIR) indicated that all the aldehyde group of the oxidized cotton fibers have reacted with amino groups of HBP-NH2. Under the selected conditions, the amount of the HBP-NH2 adsorbed or grafted onto the HCF and HGCF is about 1.52 mg/g and 3.68 mg/g respectively.The dyed HGCFs with reactive dyes in salt-free dyeing displayed markedly enhanced colour strength, and the washing fastness, rubbing fastness and leveling properties were satisfactory. In order to reveal the mechanism of salt-free dyeing on HCF and HGCF with reactive dyes, theζ-potential of HCF and HGCF in the liquid phase, dyeing thermodynamics, dyeing dynamics and hue changes of HCF and HGCF dyed with reactive dyes were examined.The antimicrobial activity the HBP-HTC aqueous solution was studied against Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus. The minimum inhibitory concentration of the HBP-HTC aqueous solution is about 20 ppm. The cotton fabric was treated with HBP-HTC aqueous solution by the impregnation method to provide it with antimicrobial properties. The antimicrobial activities of the HBP-HTC treated cotton fabrics were evaluated quantitatively. The results indicated that the HBP-HTC treated cotton fabric showed 99.92% of bacterial reduction to S. aureus and 99.66% of bacterial reduction to E. coli, respectively. The antimicrobial activities of the HBP-HTC treated cotton fabrics were maintained at over 99.00% reduction level even after being exposed to 20 consecutive home laundering conditions.Nano-silver colloidal solutions were prepared in one step by mixing AgNO3 aqueous solution and HBP-NH2 aqueous solution. The formation of silver colloid nanoparticles was characterized by Fourier Transform Infrared Spectrophotometry (FTIR), Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), UV/Visible Absorption Spectrophotometry and X-ray Diffraction (XRD). The produced silver colloidal nanoparticles have average sizes ranged from 5 to 30 nm. The antimicrobial activity of the nano-silver colloidal solutions was evaluated quantitatively against E. coli and S. aureus. The minimum inhibitory concentration of the nano-silver colloidal solution is about 3μg/ml. To provide cotton fabrics with antibacterial properties, cotton fabric samples were treated with 20 mg/l nano-silver colloidal solution by the impregnation method. The silver-treated cotton fabrics showed excellent and durable antimicrobial effect against both S. aureus and E. coli. Still over 98.77 % of bacterial reduction was maintained even after exposure to 20 consecutive home laundering conditions. In addition, the Ag-clusters on the cotton fabrics were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).All these studies indicated that hyperbranched polymer can be applied to functional modification of cotton. And these studies may widen the application fields of the hyperbranched polymer and provide a new idea for functional modification of other fibres or fabrics.