Solubility parameters and solvent affinities for polycaprolactone: A comparison of methods

Abstract

Intrinsic viscosity measurements were used in combination with the functional solubility parameter (FSP) and Hansen solubility parameter (HSP) fitting methods to determine the solubility parameters (SPs) of polycaprolactone (PCL). Despite using only eight solvents, a simple similarity criteria approach showed that the HSPs and FSPs were good predictors of the relative solvent-PCL affinity compared to HSPs available in the literature and SPs calculated using additive group contribution methods. Three complementary computational methodologies-Conductor-like Screening MOdel for Real Solvents (COSMO-RS), partial solvation parameters (PSPs), and a thermodynamic quantitative structure-property relationship (QSPR) approach-were used to substantiate the relative solvent-PCL affinities revealed by the intrinsic viscosity measurements. The solvent affinities predicted by all three techniques were in good agreement with the trend observed in the experimental intrinsic viscosity data, but the COSMO-RS activity coefficients, ln(γ PCL ), were slightly superior to the PSP and thermodynamic QSPR methods, particularly when incorporating the Elbro free-volume combinatorial correction in the COSMO-RS calculations. As part of this study, the FSP fitting algorithm was modified to obtain the PSPs for PCL in terms of the intrinsic viscosity data, thereby, presenting a promising new way to calculate the PSPs of polymers from empirical solubility and solvent affinity data.

3,4-Ethylenedioxythiophene (EDOT) End-Group Functionalized Poly-ε-caprolactone (PCL): Self-Assembly in Organic Solvents and Its Coincidentally Observed Peculiar Behavior in Thin Film and Protonated Media

“…Moreover, if the general principle that an increase in solvent polarity leads to a deshielding effect in the fully soluble parts, which results in downfield-shifting, is taken into account, the NMR investigations confirmed the known character of ACN as a poor/non-solvent for PCLs [ 61 , 62 ]. Meanwhile, the upfield-shifting of a and b aromatic protons in Chl is striking evidence of the EDOT-PCL intermolecular π–π stacking of the aromatic segment of the molecule [ 63 ] in this solvent, thus suggesting the formation of associated supramolecular structures.…”

“…The particle shapes and the AFM appearance are evidence of the formation of micelle-like structures in the solution, which probably have less soluble EDOT moiety as a core (see Table S2 for solubility parameter values) and OCL as protecting shell. These particles are expected to have enhanced stability as the OCL chains are more probable into a stable, extended conformation mediated by the hydrogen-donor character of Chl (its acidic nature), which generate favorable hydrogen-bonding interactions (cross-associations) with the nucleophilic ester groups of basic nature in OCL [ 62 ]. It appears that, from the point of view of chain conformation, the interaction of OCL with Chl has a similar result to that of the water interaction with PEG, which was explained in detail in our previous report [ 55 ].…”

“…Our claim is supported by the large difference between the affinities of the structural components of EDOT-PCL in relation to ACN. Besides the recognized marginality of ACN for PCL [ 62 ], the high miscibility of EDOT with ACN can be seen because both the dipole moment and solubility parameters of EDOT (see Table S2 ) are simultaneously closer to those of ACN [ 101 ], as compared to OCL. The fact that a spherical micellar shape is preserved in the films ( Figure 4 A) is proof that solvophobic interactions overwhelm crystallization ordering in the micelles’ inner core and that crystallization could take place in the confined spaces formed by them [ 89 , 92 ].…”

PCL/Andiroba Oil (Carapa guianensis Aubl.) Hybrid Film for Wound Healing Applications

“…Gomes [ 60 ] produced more crystalline PCL fibers, reducing the acetic acid content, using 95:5 acetic acid:water ratios. The low volatility and low chemical affinity of acetic acid with the PCL’s hydrophobic chain lead to less aggressive solubilization, affecting crystal domains’ formation [ 61 , 62 ].…”

Controlling the crystallinity and solubility of functional PCL with efficient post-polymerisation modification

“…44 Polymer solubility is an important aspect in allowing control over self-assembly behaviour, polymer microstructure and material performance. 45 While enhancing water solubility has been widely studied, increasing solubility in hydrophobic solvents is less well studied. Hence, we expected that the ability to quantitatively graft various alkyl thiols onto the PCL backbone would enable increased solubility in non-polar solvents compared to PCL.…”