End-functionalization of cellulose nanocrystals
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Journal Title
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Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
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Authors
Date
2014-06-03
Department
Major/Subject
Renewable Materials Engineering
Mcode
KM3002
Degree programme
Master's Programme in Bioproduct Technology
Language
en
Pages
61+2
Series
Abstract
Regioselective modification of nanocelluloses can have intriguing applications in self-assembled material synthesis. In this thesis, cellulose nanocrystals (CNC) were selectively functionalized at their reducing ends with thiol and maleimide groups. For thiol end-functionalization, a protocol was developed based on NHS/EDC-catalyzed coupling of NaClO2-oxidized CNCs with NH2 (CH2)6 SH in water. Maleimide end-functionalization was achieved by reacting end-thiolated CNCs (CNC SH) with a homobifunctional maleimide crosslinker in ethanol. Among the alternative protocols compared, end-thiolation was found to proceed most effectively in high ionic strength, with an EDC:NHS molar ratio of 10:1. Thus prepared CNC SH adsorbed on gold as a fairly flexible layer in quartz-crystal microbalance with dissipation (QCM D). Complying with a previous study, these results validate CNC SH preparation via a faster reaction in simpler conditions than before. The results of maleimide end-functionalization suggested 50:1 as the optimal molar ratio between the maleimide crosslinker and thiols of CNC SH. This modification lead to a slight adsorption of this sample on a surface covered with thiol groups in QCM D. However, the adsorption remained low, probably due to limited yield of the functionalization. In the future, control experiments are necessary to adequately validate the developed end-thiolation method. In addition, the maleimide end-functionalization needs to be more thoroughly optimized, particularly in ethanol media. With these improvements, both functionalization techniques could become feasible routes to prepare CNCs that attach to other molecules and surfaces in a controlled orientation.Description
Supervisor
Laine, JanneThesis advisor
Lokanathan, ArcotKeywords
cellulose nanocrystals, reducing end, functionalization