Tailor-Made, Linear, and “Comb-Like” Polyester-Based Copolymers: Synthesis, Characterization, and Thermal Behavior of Potential 3D-Printing/Electrospinning Candidates

Abstract

Tailor-made, linear, and “comb-like” poly(ε-caprolactone)-based copolymers were synthesized by employing a combination of controlled polymerization techniques. Poly(dimethylsiloxane-block-ε-caprolactone) copolymers (SCL#) were synthesized by a combination of anionic and ring-opening polymerization (ROP), whereas “comb-like” poly(hydroxyethylmethacrylate-co-(hydroxyethylmethacrylate-graft-ε-caprolactone)-block-ε-caprolactone) (HEMACL#) were synthesized through simultaneous ROP and reversible addition fragmentation chain transfer (RAFT) polymerization. Copolymers were characterized by hydrogen nuclear magnetic resonance (1H-NMR), size exclusion chromatography (SEC), and Fourier transform infrared (FTIR) spectroscopy. All polymers exhibited narrow molar masses distributions (Mw/Mn<1.54), and their thermal properties were analyzed by isothermal crystallization kinetics (Avrami’s theory, by using differential scanning calorimetry (DSC)) and by employing modulated thermogravimetric analysis (MTGA). The macromolecular structure exerts a noticeable effect on the PCL block behavior when compared to the PCL homopolymer, at least for the temperature range studied (16–24°C): less differences in thermal properties were observed for linear block copolymers, whereas for “comb-like” graft copolymers their final crystallization capacity strongly depends on the presence of branches. For both sets of copolymers, the decrease in the resulting melting temperatures and the increase in the half-life crystallization time values might be useful processing parameters, particularly if these copolymers are planned for using as an alternative source of 3D printing or electrospinning materials.

Hydroxyapatite Growth on Poly(Dimethylsiloxane-Block-ε-Caprolactone)/Tricalcium Phosphate Coatings Obtained by Electrophoretic Deposition

“…PCL homopolymer shows a T 0.05 value at 341.5 °C, becoming more noticeable after approximately 400 °C (the thermal degradation event which corresponds to polyester chain decomposition) (Cai et al, 2014;Ninago et al, 2015;Redondo, 2018). On the other hand, the following degradation events in the copolymer were detected at 193 °C (associated to the rupture of polyester chains through the ester pyrolysis reaction generating H 2 O, CO 2 , and 5-hexenoic acid); at 289 °C (associated to the PCL block decomposition); and at 366 °C (associated to the PDMS block degradation) (Persenaire et al, 2001;Ninago et al, 2013;Redondo et al, 2018). Regarding to TCP, no decomposition event was observed in the studied range.…”

“…The PDMS-b-PCL copolymer was synthesized by ROP polymerization of ε-CL monomer, according to the methodology already published by the group (Redondo et al 2018). Copolymerization was carried out in a glass reactor under the nitrogen atmosphere, by employing degassed toluene as a solvent and tin (II) 2-ethylhexanoate (Sn(Oct) 2 ) as a catalyst, at 110 °C for 24 h (Scheme 2).…”

“…Regarding to DSC measurements, PDMS-OH macroinitiator presents only a thermal transition (T mPDMS ) in the range of temperature analyzed. Besides, three thermal transitions are detected in PDMS-b-PCL copolymer: T gPCL and T mPCL of the PCL block and T mPDMS of the PDMS semi-crystalline phase (Redondo et al, 2018). Besides, % crystallinity (X c ) was obtained by taking into account the PCL content and ΔH ref 136.1 J g −1 (Yam et al, 1999).…”

“…In one of the previous work, we reported the capability of block copolymers to induce the precipitation of a HA layer (Redondo et al, 2018;Ninago et al, 2020;Redondo et al, 2020). In this sense, the effect of molecular architecture (linear or branched) of block copolymers and the use of Bioglass ® on EPD tests (t 6 min) was analyzed.…”