Copolymerization of Caprolactone Isomers to Obtain Nanoparticles with Constant Hydrophobicity and Tunable Crystallinity

Abstract

To obtain a set of polycaprolactones (PCL) with varying crystallinity, the triazabicyclodecene-catalyzed copolymerization of the two constitutional isomers ε-caprolactone (εCL) and δ-caprolactone (δCL) was carried out at room temperature in toluene. Variation of the feed fraction of εCL from 50% to 80% and the detailed kinetic studies accompanied by application of terminal as well as nonterminal kinetic models suggested the formation of random copolymers. Differential scanning calorimetry and wide-angle X-ray scattering investigations revealed the decrease of melting temperatures and degree of crystallinity with the εCL fraction in the PCL. All copolymers were suited to obtain aqueous nanoparticle dispersions by means of nanoprecipitation. Encapsulation of the fluorescent probe pyrene confirmed a constant hydrophilic/hydrophobic balance of the nanoparticles.

Effect of Crystallinity on the Properties of Polycaprolactone Nanoparticles Containing the Dual FLAP/mPEGS-1 Inhibitor BRP-187

“…In our previous study, five poly(εCL- ran -δCL) copolymers, herein named ε87-δ13, ε81-δ19, ε75-δ25, ε61-δ39 and ε45-δ55, and the two respective homopolymers PεCL and P δ CL, herein referred to as ε100-δ0 and ε0-δ100, were synthesized exhibiting a constant HHB [ 17 ]. It was demonstrated that the HHB of the bulk polymers correlated with the HHB of the corresponding NPs when particles were prepared in THF using a polymer concentration of 1 mg mL −1 [ 17 ].…”

“…In our previous study, five poly(εCL- ran -δCL) copolymers, herein named ε87-δ13, ε81-δ19, ε75-δ25, ε61-δ39 and ε45-δ55, and the two respective homopolymers PεCL and P δ CL, herein referred to as ε100-δ0 and ε0-δ100, were synthesized exhibiting a constant HHB [ 17 ]. It was demonstrated that the HHB of the bulk polymers correlated with the HHB of the corresponding NPs when particles were prepared in THF using a polymer concentration of 1 mg mL −1 [ 17 ]. In the present study, the particle formation of the ε100-δ0 and ε0-δ100 was investigated over a wider range of polymer concentrations in THF ranging from 0.25 to 10 mg mL -1 using an automated pipetting robot that was adapted for the HT-nanoprecipitation [ 25 ].…”

“…The PCL homopolymers and P(εCL- ran -δCL) copolymers were synthesized as previously reported [ 17 ]. Key characterization data are listed in Table S1 in the Supplementary Information (SI) .…”

“…Key characterization data are listed in Table S1 in the Supplementary Information (SI) . For further details on their synthesis, the reader is referred to literature reports [ 17 ]. Polyvinylalcohol (PVA) (Mowiol 4-88), tetrahydrofuran (THF), dimethylsulfoxide (DMSO) and lipase from the yeast Candida rugosa were purchased from Sigma-Aldrich (Germany).…”

“…Thus, PCL represents a promising candidate to design materials with tailor-made properties [ 13 , 15 , 16 ]. Bandelli et al recently demonstrated that copolymerization of the constitutional isomers ε-caprolactone (εCL) and δ-caprolactone (δCL) with a varying ratio of εCL and δCL can generate a library of five copolyesters featuring a constant HHB and similar molar masses in the range of 7 to 10 kDa, but the copolymers showed a varying crystallinity [ 17 ]. They are hence suitable materials to study the sole influence of crystallinity on the particle properties and performance.…”