Browsing by Author "Witharana, Dilmi"

The use of natural dyes and pigments is a practice that dates back to the beginning of civilization. With the invention of synthetic dyes, these natural dyeing practices gradually decreased due to the convenient synthesis methods and wider range of applications of synthetic dyes. However, in recent years, bio-based colourants are starting to gain more attention as green alternatives to synthetic dyes which have limitations such as environmental persistency and low biodegradability. Nevertheless, natural dyes have poor brightness and fastness properties that they tend to fade easily. To overcome these limitations, organic modifications can be done to natural colour molecules which can bring about better interactions with textile fibres. This also helps to eliminate the use of metalated mordants in the dyeing process, reducing the environmental impact. The aim of this study was to modify bio-based dyes to have better interactions with natural fibres such as wool and cellulose. This thesis will mainly focus on non-covalent dye fibre interactions. Dyes with acidic functionalities show interactions with natural fibres such as wool whereas dyes with basic functionalities interact better with cellulose fibres. Natural dyes such as quercetin, emodin and alizarin can be modified such that one or more of their hydroxyl groups are substituted with an organic moiety with various functionalities. Click chemistry is a convenient strategy to introduce these new functionalities to colour compounds. The organic moiety can be modified to achieve hydrophobicity, hydrophilicity, acidity or basicity to accommodate the dyeing process and the nature of the textile. Thus, these modified bio-based colourants offer a broader scope for potential dyeing applications.