Solid-state NMR to quantify surface coverage and chain length of lactic acid modified cellulose nanocrystals, used as fillers in biodegradable composites

Gårdebjer, Sofie; Bergstrand, Anna; Idström, Alexander; Börstell, Camilla; Naana, Stefan; Nordstierna, Lars; Larsson, Anette

doi:10.1016/j.compscitech.2014.11.014

Cited by 80 publications

(58 citation statements)

References 38 publications

(51 reference statements)

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“…CP-MAS solid state 13 C-NMR is a versatile tool that is useful for assessing modifications to CNCs. 23,51,52 Hence, this method was used to further characterize citrate-, malonate and malate CNCs. All CP-MAS solid state 13 C-NMR spectra of modified and unmodified CNCs in Figure 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Also, for simplicity, esterification is shown occurring exclusively at C6 41,55 although it is understood that esterification at C2 and C3 will also occur.…”

Section: Characterization Of Modificationmentioning

confidence: 99%

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

Spinella

Maiorana

Qian

et al. 2016

ACS Sustainable Chem. Eng.

176

111

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Cellulose nanocrystals (CNCs) were modified with natural di-and tricarboxylic acids using two concurrent acid-catalyzed reactions including hydrolysis of amorphous cellulose segments and Fischer esterification, resulting in the introduction of free carboxylic acid functionality onto CNC surfaces. CNC esterification was characterized by Fourier Transform Infrared Spectroscopy, 13 C solid state magic-angle spinning (MAS) and conductometric titration experiments. Average degree of substitution values for malonate, malate, and citrate CNCs are 0.16, 0.22 and 0.18, respectively. Despite differences in organic acid pKa, optimal HCl cocatalyst concentrations were similar for malonic, malic and citric acids. After isolation of modified CNCs, residual cellulose co-products were identified that are similar to microcrystalline cellulose based on SEM and XRD analysis. As proof of concept, recycling experiments were carried to increase the yield of citrate CNCs. The by-product was then recycled by subsequent citric acid/HCl treatments that resulted in 55% total yield of citrate CNCs.The crystallinity, morphology, and substitution of citrate CNCs from recycled cellulose coproduct is similar to modified citrate CNCs formed in the first reaction cycle. Thermal stability of all modified CNCs under air and nitrogen resulted in T 10% and T 50% values above 256 °C and 323 °C, respectively. Thus, they can be used for melt-processing operations performed at moderately high temperatures without thermal decomposition. Nanocomposites of polyvinyl alcohol with modified CNCs (1 wt% malonate-, malate-, citrate and unmodified CNCs) wereprepared. An increase in the thermal decomposition temperature by almost 40 °C was obtained for PVOH-citrate modified CNC nanocomposites.Furthermore, since TGA determined weight loss up to 150°C is attributed to loss of bound water, this provides a tool to determine CNC water affinity. By 150°C, the weight loss of modified and non-modified CNCs is 6% and 2%, respectively. Consequently, modified CNCs with surface carboxylate groups have higher water affinity than non-modified CNCs. Moreover, significant differences in the thermal stability are observed as a function of the di-or triacid used for CNC modification. Based on the peaks of the derivative thermogravimetric curve (DTG, T 50% ), modified CNCs have the following thermal stability: malonate = HCl > malate > citrate CNCs.Corresponding values for T 50% are 366°C, 365°C, 350°C and 345°C, respectively. The amount of residual char at 600°C for HCl, malonate, malate and citrate CNCs is 8, 13, 16 and 20%, respectively. Hence, it follows that increasing the T 50% for di-and tri-acid modified CNCs results in correspondingly lower char formation. Increased char amounts is likely due to CNC functionalizations that lead to relatively larger number of cross-linking events at elevated temperatures.Since the exclusion of air during melt processing is generally not practical, the effect of CNC modification on thermal stability in air was also determined and the correspo...

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Section: Characterization Of Modificationmentioning

confidence: 99%

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

Spinella

Maiorana

Qian

et al. 2016

ACS Sustainable Chem. Eng.

176

111

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“…Gårdebjer et al produced nanocomposite films with up to 20 wt% of desulfated CNC and chemically modified with PLA. Both modified and unmodified CNC were incorporated as fillers in three different biodegradable materials: polylactide acid (PLA), poly(lactide‐ co ‐glycolide) (PLGA), and PHB via solvent casting.…”

Section: Polymersmentioning

confidence: 99%

Functionalized cellulose nanocrystals as reinforcement in biodegradable polymer nanocomposites

et al. 2017

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This review describes the use of cellulose nanocrystals (CNC) as fillers in biodegradable polymer matrices over the past few years. The preparation and characterization of CNC‐based nanocomposites are highlighted here with a focus on thermophysical and mechanical properties. The characterization and isolation of nanocellulose from different raw material sources are discussed in detail, as well as different surface modifications. The addition of CNC in biodegradable polymer, combined with nanocellulose surface engineering and driven by sustainability trends, has the potential to impact various industrial sectors. POLYM. COMPOS., 39:E9–E29, 2018. © 2017 Society of Plastics Engineers

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“…From the C4 13 C signals, square cross-sectional cellulose models of elementary fibrils and fibril aggregates have been proposed for native (Larsson et al, 1997;Wickholm et al, 1998), and for regenerated cellulose (Zuckerstätter et al, 2013), respectively. Using these models, dimensions of elementary fibrils and fibril aggregates (Gårdebjer et al, 2015;Newman, 1999;Wickholm et al, 1998), crystallinity index (CI) (Lee et al, 2016;Park, Johnson, Ishizawa, Parilla, & Davis, 2009) as well as specific surface area (Chunilall, Bush, Larsson, Iversen, & Kindness, 2010) have been estimated and structural changes of the material, for example upon drying and rewetting, have been monitored (Idström, Brelid, Nydén, & Nordstierna, 2013;Östlund, Idström, Olsson, Larsson, & Nordstierna, 2013). Equivalent features, with 13 C signals originating from different parts of the fibril model should also be observed for the other 13 C atoms in the AGU, though these have been more difficult to assign due to signal overlap.…”

Section: Introductionmentioning

confidence: 99%

13C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy

Idström

Schantz

Sundberg

et al. 2016

Carbohydrate Polymers

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From the assignment of the solid-state (13)C NMR signals in the C4 region, distinct types of crystalline cellulose, cellulose at crystalline surfaces, and disordered cellulose can be identified and quantified. For regenerated cellulose, complete (13)C assignments of the other carbon regions have not previously been attainable, due to signal overlap. In this study, two-dimensional (2D) NMR correlation methods were used to resolve and assign (13)C signals for all carbon atoms in regenerated cellulose. (13)C-enriched bacterial nanocellulose was biosynthesized, dissolved, and coagulated as highly crystalline cellulose II. Specifically, four distinct (13)C signals were observed corresponding to conformationally different anhydroglucose units: two signals assigned to crystalline moieties and two signals assigned to non-crystalline species. The C1, C4 and C6 regions for cellulose II were fully examined by global spectral deconvolution, which yielded qualitative trends of the relative populations of the different cellulose moieties, as a function of wetting and drying treatments.

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Solid-state NMR to quantify surface coverage and chain length of lactic acid modified cellulose nanocrystals, used as fillers in biodegradable composites

Cited by 80 publications

References 38 publications

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

Functionalized cellulose nanocrystals as reinforcement in biodegradable polymer nanocomposites

13C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy

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