NEW INSIGHTS INTO THE MATERIAL CHEMISTRY OF POLYCAPROLACTONE-GRAFTED CELLULOSE NANOFIBRILS / POLYURETHANE NANOCOMPOSITES
C.Tiana, S. Y. Fua*, Q. J. Menga and Lucian A Lucia a,b
aState Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China 510640
bKey Laboratory of Pulp & Paper Science and Technology, Qilu University of Technology, Jinan, PR China 250353
* Corresponding author:
Preparation of TONCs
Approximately 5 g (o.d.) of cotton linters was dispersed in deionized water at 1% (w/v). Predetermined amounts of TEMPO (0.015 g/g o.d.p.) and NaBr (0.1 g/g o.d.p.) were added to the slurry. NaClO solution (6%, 25 mmol) was then added to the mixture and the TEMPO-mediated oxidation was initiated. The oxidation was conducted at 25 °C and the pH was maintained at 10 ± 0.2 by the addition of 0.5 M NaOH solution. The reaction was quenched by adding ethanol (10 mL) when no further decrease of pH were observed. After washed and dialyzed with deionized water, the aqueous suspension of TONCs was obtained by ultrasonicating for 20 min using an ultrasonic homogenizer (KBS-1200, China) with an output power of 1200 W.
Grafting of PCL to TONCs via ROP
Stoichiometric ε-CL and 2 wt-% (with respect to ε-CL) of Sn(Oct)2 were slowly added into the toluene suspension under a blanket of nitrogen. The polymerization was conducted at 100°C for 24 h. After cooling to room temperature, the PCL-grafted TONC was recovered by precipitating the mixture into carbinol. The product was then washed and Soxhlet extracted for in dichloromethane to remove unreacted ε-CL and homo-PCL. The final product was obtained after vacuum drying 45°C for 48 h.
Sample preparation for HSGC
Samples were soaked in 0.1 M HCl at RT for 1 h, and washed thoroughly with deionized water. The groups -COONa in TONC were converted to -COOH which were measured by HSGC.
Sample preparation for TEM
One droplet of 0.01% TONCs suspension was distributed on the surface of the copper grid (200 mesh). The samples were negative stained by of 3% phosphotungstic acid solution.
Test procedure of CA
Samples were grounded to powders and compressed under a pressure of 10 bar using an IR press, to obtain smooth surfaces. Then a droplet of 5∼10 μL ultrapure water was dropped on the surface of the sample. A Young-Laplace profile was used to analyze the CA results.
Sample preparation and test procedure of AFM
A droplet of the PTONC and CLPU mixture dispersed in DMSO was spread onto a fresh mica substrate and dried at 80°C for 12 h. All samples were observed in tapping mode under ambient conditions, using a Bruker Multimode 8 (America) instrument. The spring constants of the silicon tip was 20-80 N/m, while the resonance frequency was approximately 298-335 kHz.
The temperature gradient and respective heating rates of DSC: first, from RT to 150 °C with a heating rate of 10 °C/min, then isotherm for 10 min, from 150 to -10 °C at 10 °C /min, isotherm for 10 min, and ending with a heating cycle from -10 to 150 °C at 5°C/min.
Figure S1FTIR spectra of unmodified TONC and PCL modified PTONC with different monomer content.
Figure S213C-NMR spectra of TONC
Figure S3 TEM images of (a) TONCs and (b) PTONC-10
Figure S4DTG curves of TONCs before and after grafting
Figure S5DSC curves of TONCs before and after grafting
Figure S6AFM height images of (a) TONC/CLPU-1, (b) TONC/CLPU-5
Figure S7DMA curves of PTONC/CLPU-5and TONC/CLPU-5 nanocomposites (a: storage modulus, b: loss factor)
Figure S8SEM images of fracture morphologies of TONC/CLPU nanocomposites after stretch.