Determining conformational order and crystallinity in polycaprolactone via Raman spectroscopy

Abstract

Raman spectroscopy is a popular method for non-invasive analysis of biomaterials containing polycaprolactone in applications such as tissue engineering and drug delivery. However there remain fundamental challenges in interpretation of such spectra in the context of existing dielectric spectroscopy and differential scanning calorimetry results in both the melt and semi-crystalline states. In this work, we develop a thermodynamically informed analysis method which utilizes basis spectra – ideal spectra of the polymer chain conformers comprising the measured Raman spectrum. In polycaprolactone we identify three basis spectra in the carbonyl region; measurement of their temperature dependence shows that one is linearly proportional to crystallinity, a second correlates with dipole-dipole interactions that are observed in dielectric spectroscopy and a third which correlates with amorphous chain behavior. For other spectral regions, e.g. C-COO stretch, a comparison of the basis spectra to those from density functional theory calculations in the all-trans configuration allows us to indicate whether sharp spectral peaks can be attributed to single chain modes in the all-trans state or to crystalline order. Our analysis method is general and should provide important insights to other polymeric materials.

Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications

“…In most cases, Raman scattering is sensitive to the degree of crystallinity in a sample. Typically a crystalline material yields a spectrum with very sharp, intense Raman peaks, whilst an amorphous material will show less intense Raman peaks 46 – 48 . Table 1 and Fig.…”

Effect of processing conditions on crystallization kinetics during materials extrusion additive manufacturing

“…The Raman spectra in the carbonyl (C=O) stretch region of the spectrum are analyzed to determine crystallinity using a method developed previously. [22] Briefly, we fit the experimental spectra to a set of three basis spectra that account for chains in an amorphous conformation, chain-chain dipole interactions, and chains ordering in a crystalline lattice. The integrated intensity of the crystalline basis spectrum normalized by the total integrated intensity of the C=O stretch region is directly proportional to the crystallinity as measured by DSC.…”

“…[21] In our prior work, we developed a linear relationship between the Raman spectrum of PCL and crystallinity. [22] Raman probe techniques should therefore be a viable in-line method for measuring crystallinity in material extrusion processes.…”

Polycaprolactone-Based, Porous CaCO3 and Ag Nanoparticle Modified Scaffolds as a SERS Platform With Molecule-Specific Adsorption

“…4-MBA has a high affinity to silver nanoparticles through the thiol group. But, there was no signal of 4-MBA (10 −3 M) on PCL scaffolds without CaCO 3 (Figure 2A, the violet and bottom line), while all of the present peaks correspond to PCL (Kotula et al, 2017). After the mineralization procedure, there was an additional peak at 1,583 cm −1 corresponding to the 4-MBA ν(C-C) ring mode (Orendorff et al, 2005).…”