<p>Weak wet strength of paper is one of the major challenges limiting the increase use of paper products. It is difficult to form strong adhesive joints between hydrophilic wet cellulose surfaces. Previous research disclosed an approach using polyvinylamine (PVAm) with grafted TEMPO for oxidation of cellulose to improve wet cellulose adhesion. The object of this research is to further develop new and more eco-friendly approaches to induce adhesion between wet cellulose surfaces. PVAm-graft-TEMPOs (PVAm-TEMPO) with various TEMPO grafting extents were prepared and characterized by electron paramagnetic resonance (EPR) and conductometric titration. The stability studies of fully hydrolysed PVAm in sodium hypochlorite (NaClO) environment were conducted. PVAm can be oxidized and degraded by NaClO in alkaline solution. Furthermore, PVAm-TEMPO was applied into the TEMPO/laccase/O2 oxidation of cellulose. Increased wet adhesion between cellulose surfaces were achieved with this enzyme catalyzed approach and the mechanism of this approach was investigated. PVAm-TEMPO and laccase works together as mediators catalyzing the oxidation of primary alcohol groups on cellulose into aldehyde groups that react to form covalent bonds with primary amines on PVAm. However, cationic PVAm-TEMPO and anionic laccase can form complexes during the oxidation process. Grafted TEMPO in enzyme catalyzed approach offers three significant advantages over small molecule TEMPO (free TEMPO). First, as PVAm has high molecular weight, the oxidation of porous fibers is restricted to the exterior surfaces only, which avoids the excessive oxidation of interior surfaces and prevents from weakening the mechanical property of fibers. Second, TEMPO is concentrated on cellulose surfaces by tethered it to PVAm, compared with water-soluble free TEMPO. Thus the total dose of TEMPO required to oxidize fibers by PVAm</p> / Master of Applied Science (MASc)

Plasma-based surface modifications offer many interesting possibilities for the production of high value-added polymeric materials. In this work, different plasma-based synthetic concepts were employed to endow poly(ethylene terephthalate) (PET) fabrics with accessible amine functionalities. These concepts were compared to find out the appropriate engineering methods, which can be further accepted by textile industries to overcome the limited reactivity of PET fabric surfaces, while the bulk characteristics are kept unaffected. Amine functionalities were introduced onto the surface of PET fabrics using either low-pressure ammonia plasma treatment or coating oxygen plasma-treated PET fabric with cationic polyelectrolytes. Two different cationic polyelectrolytes were used in this study namely poly(diallyldimethylammonium chloride) as an example of strong polyelectrolytes and poly(vinyl amine-co-vinyl amide) as an example of weak polyelectrolytes. The modified surfaces were characterized by a combination of various surface-sensitive techniques such as X-ray photoelectron spectroscopy (XPS), electrokinetic measurements and time-dependent contact angle measurements. Furthermore, the amine functionalities introduced by different surface modifications were used for the subsequent immobilization of various classes of anionic dyes to evaluate the efficiency of different surface modifications. Color strength (K/S) and fastness measurements of colored fabrics were also explored. Their results can be taken as a measure of the extent of the interaction between different modified surfaces and anionic dyes. Finally, it was demonstrated that anchoring poly(vinyl amine-co-vinyl amide) layer onto PET fabric surfaces modified with low-pressure oxygen plasma is an efficient approach to improve coloration behavior and to overcome different problems related to PET fabrics coloration, such as coloration of PET/wool blend fabric with a single class of dyes. This is a crucial step towards the substrate independent surface coloration, which becomes dependent on the properties of the top layer rather than chemical structure of the fibers.

Plasma-based surface modifications offer many interesting possibilities for the production of high value-added polymeric materials. In this work, different plasma-based synthetic concepts were employed to endow poly(ethylene terephthalate) (PET) fabrics with accessible amine functionalities. These concepts were compared to find out the appropriate engineering methods, which can be further accepted by textile industries to overcome the limited reactivity of PET fabric surfaces, while the bulk characteristics are kept unaffected. Amine functionalities were introduced onto the surface of PET fabrics using either low-pressure ammonia plasma treatment or coating oxygen plasma-treated PET fabric with cationic polyelectrolytes. Two different cationic polyelectrolytes were used in this study namely poly(diallyldimethylammonium chloride) as an example of strong polyelectrolytes and poly(vinyl amine-co-vinyl amide) as an example of weak polyelectrolytes. The modified surfaces were characterized by a combination of various surface-sensitive techniques such as X-ray photoelectron spectroscopy (XPS), electrokinetic measurements and time-dependent contact angle measurements. Furthermore, the amine functionalities introduced by different surface modifications were used for the subsequent immobilization of various classes of anionic dyes to evaluate the efficiency of different surface modifications. Color strength (K/S) and fastness measurements of colored fabrics were also explored. Their results can be taken as a measure of the extent of the interaction between different modified surfaces and anionic dyes. Finally, it was demonstrated that anchoring poly(vinyl amine-co-vinyl amide) layer onto PET fabric surfaces modified with low-pressure oxygen plasma is an efficient approach to improve coloration behavior and to overcome different problems related to PET fabrics coloration, such as coloration of PET/wool blend fabric with a single class of dyes. This is a crucial step towards the substrate independent surface coloration, which becomes dependent on the properties of the top layer rather than chemical structure of the fibers.