Abstract:

Attachment of grafted PCL-b-POEGMA on SiO2 NPs was confirmed via thermogravimetric analysis (TGA) decomposition events in comparison to the linear free polymer analogue. IR (infrared analysis) was performed and it showed an increase in carbonyl and CH2 content, with a decrease in hydroxyl content as subsequent blocks were grafted from the NPs. Light scattering was used for confirmation of size changes in solution by Rh and/or Rg values in various solvents. Light scattering analysis also included size changes upon hydrocarbon uptake.

Suggested Citation:

Keller, Christopher. 2020. Infrared analysis, thermogravimetric analysis, and light scattering of grafted PCL-b-POEGMA on SiO2 NPs. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-58bp-tk87

Publications:

Keller, C. B., Walley, S. E., Jarand, C. W., He, J., Ejaz, M., Savin, D. A., & Grayson, S. M. (2021). Synthesis of poly(caprolactone)-block-poly[oligo(ethylene glycol)methyl methacrylate] amphiphilic grafted nanoparticles (AGNs) as improved oil dispersants. Polymer Chemistry, 12(33), 4758–4769. doi:10.1039/d1py00418b

Purpose:

This experiment was carried to determine the nature of bonds arising from the amphiphilic copolymers from the surface of the silica nanoparticles; to quantify the amount of organic polymer present by percent weight relative to the nanoparticle, and to Illustrate the amphiphilic behavior of the copolymers through size changes in different solvent environments.

Data Parameters and Units:

This dataset consists of FTIR (Fourier-transform infrared spectroscopy) data, DLS (Dynamic Light Scattering) data and TGA spectra showing the bare SiO2 particles and various modifications to the surface such as SiO2-GPS-OH, SiO2-GPS-PCL-OH, SiO2-GPS-PCL-Br, SiO2-GPS-PCL-POEGMA-Br, and SiO2-GPS-PCL-POEGMA. Measurements for TGA data are presented in the form of percent weight loss over a range of temperatures (˚C). The headers for the spreadsheets containing TGA spectra are Time (min), Temperature (˚C), Weight (mg), Weight (%), Deriv. Weight (% / °C). F TIR data is presented in the form of wavenumbers (cm-1) to arbitrary absorbance intensity from 400 to 4000 cm-1 wavenumbers. The headers for the spreadsheets containing FTIR data are DLS data is presented as Rh calculated in nm taken from a plot of gamma vs. q2. The headers are Mutual diffusion coefficient (Dm), Hydrodynamic radius (Rh), THF eta and Gamma. DLS measurements show the size of several SiO2-GPS-PCL-POEGMA-Br NPs in various solvents.

Methods:

Thermogravimetric analysis data was collected in a tared 100 μL platinum sample pan, ramping from 25˚C to 600˚C at a rate of 5 ˚C/min under inert nitrogen atmosphere, following by isothermal hold at 600 ˚C for 30 min. For the case of the nanoparticles dispersed in deionized water, and those that have been exposed to oil in deionized water, samples were ramped 5˚C/min from 25˚C to 100˚C in inert nitrogen atmosphere and held at a 100˚C for 5 min isothermally to remove all presence of water, followed by data collection from 100˚C to 500˚C at a ramp rate 10˚C/min in an “air” atmosphere. Measurements are presented in the form of percent weight loss over a range of temperatures (˚C). An iS50 ATR-FTIR was used to collect Fourier Transform Infrared Spectroscopy (FTIR) measurements. A 32-scan background was collected immediately prior to each sample. Measurements were conducted with 3 mg of sample over 64 repetitive scans. Data is presented in the form of wavenumbers (cm-1) to arbitrary absorbance intensity from 400 to 4000 cm-1 wavenumbers. A Thermo Nicholet NEXUS 670 FTIR E.S.P. was used to collect Fourier Transform Infrared Spectroscopy (FTIR) measurements. Samples were made up into potassium bromide (KBr) pellets at a concentration of 5 mg of sample per 100 mg of KBr. The mixture was ground via mortar and pestle and dried under high vacuum. A 32-scan background was collected immediately prior to each sample. Samples were placed in an inert nitrogen chamber and allowed to equilibrate for 5 minutes before collecting measurements. Measurements were collected in absorbance over 64 scans. Data is presented in the form of wavenumbers (cm-1) to arbitrary absorbance intensity from 400 to 4000 cm-1 wavenumbers. Dynamic Light Scattering (DLS) analysis was performed on fluctuations in the scattering intensity were measured via an ALV/LSE-5004 multiple tau digital correlator, and analyzed via the intensity autocorrelation function (g(2)τ). Decay rates, Γ, were obtained from single-exponential fits using a second-order cumulant analysis, and the mutual diffusion coefficient, Dm, was calculated through the relation: Γ = Dm q2, where q2 is the scalar magnitude of the scattering vector. The hydrodynamic radius (Rh) was calculated through the Stokes-Einstein equation. Light scattering measurements were performed at 25 °C, with samples were diluted to 1 mg/mL in water or THF and passed through a 0.45 μm poly(ether sulfone) or poly(vinylidene fluoride) syringe filter into a pre-cleaned, borosilicate test tube for analysis.

Instruments:

Thermogravimetric analysis was completed on a Thermo Scientific Q500 TGA. An iS50 ATR-FTIR & Thermo Nicholet NEXUS 670 FTIR E.S.P. were used to collect Fourier Transform Infrared Spectroscopy (FTIR) measurements. The iS50 FTIR was equipped with a DTGS-ATR detector, diamond crystal, and XT-KBr beamsplitter. Instrument parameters were set to a gain of 1, data spacing 0.482 cm-1, resolution 4, absorbance format, optical velocity of 0.4747, and aperture size of 100.Dynamic light scattering (DLS) analysis was performed on an ALV/CGS-3 four-angle, compact goniometer system (Langen, Germany), which consisted of a 35 mW HeNe linear polarized laser operating at a wavelength of λ = 632.8 nm and scattering angles from θ = 30-150°.

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