Browsing by Author "Koppolu, Rajesh"

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Injectable thiol-ene hydrogel of galactoglucomannan and cellulose nanocrystals in delivery of therapeutic inorganic ions with embedded bioactive glass nanoparticles
(2022-01-15) Wang, Qingbo; Xu, Wenyang; Koppolu, Rajesh; van Bochove, Bas; Seppälä, Jukka; Hupa, Leena; Willför, Stefan; Xu, Chunlin; Wang, Xiaoju
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We propose an injectable nanocomposite hydrogel that is photo-curable via light-induced thiol-ene addition between methacrylate modified O-acetyl-galactoglucomannan (GGMMA) and thiolated cellulose nanocrystal (CNC-SH). Compared to free-radical chain polymerization, the orthogonal step-growth of thiol-ene addition allows a less heterogeneous hydrogel network and more rapid crosslinking kinetics. CNC-SH reinforced the GGMMA hydrogel as both a nanofiller and a crosslinker to GGMMA resulting in an interpenetrating network via thiol-ene addition. Importantly, the mechanical stiffness of the GGMMA/CNC-SH hydrogel is mainly determined by the stoichiometric ratio between the thiol groups on CNC-SH and the methacrylate groups in GGMMA. Meanwhile, the bioactive glass nanoparticle (BaGNP)-laden hydrogels of GGMMA/CNC-SH showed a sustained release of therapeutic ions in simulated body fluid in vitro, which extended the bioactive function of hydrogel matrix. Furthermore, the suitability of the GGMMA/CNC-SH formulation as biomaterial resin to fabricate digitally designed hydrogel constructs via digital light processing (DLP) lithography printing was evaluated.
On Laccase-Catalyzed Polymerization of Biorefinery Lignin Fractions and Alignment of Lignin Nanoparticles on the Nanocellulose Surface via One-Pot Water-Phase Synthesis
(2021-07-05) Wang, Luyao; Tan, Liping; Hu, Liqiu; Wang, Xiaoju; Koppolu, Rajesh; Tirri, Teija; van Bochove, Bas; Ihalainen, Petri; Sobhana Seleenmary Sobhanadhas, Liji; Seppälä, Jukka V.; Willför, Stefan; Toivakka, Martti; Xu, Chunlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Two series of well-defined lignin fractions derived from birch and spruce alkaline lignin (AL) by sequential solvent fractionation (i-PrOH-EtOH-MeOH) were engaged in a structure–property-application relationship study. The bacterial-derived alkaliphilic laccase (MetZyme) extensively catalyzed the oxidation and polymerization of AL fractions in an aqueous alkaline solution (pH 10). Lignin fractions with low molar mass reached a higher polymerization degree due to more phenolic-OH groups serving as reactive sites of oxidation and better lignin-laccase accessibility arose from a lower lignin condensation degree than the high molar mass ones. In comparison, AL fractions from spruce were found to be less reactive toward the laccase-catalyzed polymerization than those from birch, which was attributed to the much pronounced aryl-vinyl moieties’ oxidation. Furthermore, in situ polymerization of birch AL fractions using microfibrillated cellulose as a structural template was conducted in an aqueous medium and a dispersion of nanocellulose with its fiber network evenly coated by aligned lignin nanoparticles was obtained. The present study not only provides fundamental insights on the laccase-assisted oxidation and polymerization of lignin but also presents a new perspective for valorizing lignin in biobased fiber products through green processing of solvent fractionation and enzymatic treatment.
Suberin-based dispersion coatings for moisture barrier in packaging applications
(2024-06-11) Oravala, Ilmari
Kemian tekniikan korkeakoulu | Master's thesis
A current trend in the packaging industry is to produce more easily recyclable packaging solutions. One of the main goals is to reduce plastic waste accumulation. Roughly 40 % of all plastic is used in packaging. Thus, having barrier materials which are more sustainable are highly desired. Along with having polymers with better end-of-life or recovery schemes, bio-based polymers are also in interest due to the limitations of petroleum resources. Various bio-based materials have gained interest as potential barrier materials, such as suberin, which is a lipophilic biopolyester found in the bark of certain trees. This master’s thesis explores preparation of suberin dispersions with varying pigment concentrations and investigates the barrier performance of paperboard and paper coated with the prepared suberin dispersions. The suberin used in this work was extracted from birch outer bark. Two types of pigments were used in the suberin-pigment dispersions: kaolin and talc. The pigment ratio varied from 0 to 60 wt%. The experimental work tries to find answers to how varying pigment ratios for both kaolin and talc affect the following properties: particle size, water vapor transmission rate (WVTR), water absorption (Cobb60), grease barrier (KIT) and water contact angles (WCA) of the coated paperboards and papers. One of the key observations is to find the critical pigment volume concentration (CPVC) of the coatings from the obtained WVTR results. As a side project for the experimental part, plain suberin dispersion was also coated in pilot scale on same substrates with an off-machine coater. WVTR and water absorption were measured from pilot scale coated substrates. Plain suberin and suberin-pigment dispersions were prepared and coated on paperboard and paper successfully. Overall, the barrier properties of the coated paperboards and papers were improved. The one property that was decreased, for all samples, in the terms of barrier performance was WCA. Furthermore, water absorbance (Cobb60) of all coated paper samples was increased compared to the uncoated paper.