## 3 Experimental Section
### Measurements  
\({}^{1}\)H and \({}^{13}\)C NMR spectra of the PCL diols and PUs were recorded on a Varian 300 MHz spectrometer using CDCl\({}_{\rm s}\) or DMSO-\(\rm d\)s as a solvent. Tetramethylsilane was served as the internal standard. The FTIR spectra were measured from KBr pellets (PerkinElmer spectrometer, PerkinElmer, Warsaw, Poland).  
The molar mass and molar mass distributions of the PCL diols were determined using a GPC instrument (GPC Max + TDA 305, Viscotek, Malvern, UK) equipped with Jordi DVB Mixed Bed columns (one guard and two analytical, Viscotek) at 30 \({}^{\circ}\)C in CH\({}_{2}\)Cl\({}_{2}\) (HPLC grade, Sigma-Aldrich, Poznan, Poland) at a flow rate of 1 mL/min with RI detection and calibration based on narrow PS standards (ReadyCal Set, Fluka). The results were processed using the OmniSEC software (ver. 4.7) (Viscotek).  
The MALDI-TOF MS spectra were performed in linear mode on an ultrafileXtreme(tm) (Bruker Daltonics, Poznan, Poland) mass spectrometer using a nitrogen gas laser and HABA as a matrix. The polymer samples were dissolved in tetrahydrofuran (THF) (5 mg/mL) and mixed with a solution of HABA.  
Polymer viscosity was measured in DMF (at 30 \({}^{\circ}\)C) on a Stabinger Visometer SVM 3000 ([PERSON]'s, Graz, Austria). The concentrations of the PU solutions in DMF were 0.2%, 0.4%, 0.6%, 0.8% and 1%. The viscosity-average molecular weight was calculated with the Mark-Houwink equation using the following constants: K = 6.80 \(\times\) 10\({}^{-5}\) dL/g and \(\alpha\) = 0.86 [34].  
The surface morphologies were studied by scanning electron microscope (SEM, LEO 435 VP (Zeiss, Jena, Germany)) so as to compare them with the initial morphologies.  
The fail stress (\(Fs\)), stress at 100% elongation (\(S_{100}\)), elongation at break (\(\varepsilon\)) and Shore'a hardness (\(Sh_{H}\)) of the PU samples were measured using a Zwick model 1445 tester. \(Fs\), \(S_{100}\) and \(\varepsilon\) were determined according to national standard PN-ISO 37:2007. \(Sh_{H}\) was determined according to national standard PN-80/C-04238 [35].  
The density and porosity values of the PU composites were measured by the liquid displacement method [36]. Ethanol (EtOH) was used as the displacement liquid. A dry composite sample was placed in a cylinder filled with a predetermined volume of EtOH (\(V_{1}\)). Next, the cylinder was placed _in vacuo_ for 20 min. The total volume of EtOH containing the composite sample was recorded as \(V_{2}\) and the residual EtOH volume was recorded as \(V_{3}\). Three individual measurements were performed and then the average value was calculated.  
The amount of open pores in the PU composites (\(P\)) was calculated according to the following equation:  
\[P\left(\%\right)=(V_{1}-V_{3})/(V_{2}-V_{3})\times 100\%\]  
where \((V_{2}-V_{3})\) denotes the total volume of the composite sample and \((V_{1}-V_{3})\) denotes the volume of ethanol retained in the composite sample.  
The density of the composite (\(d\)) was expressed as:  
\[d=W/(V_{2}-V_{3})\]  
where \(W\) refers to the weight of the sample.  
The quantity of the released CLO was analysed by means of HPLC CAD using the UHPLC Dionex Ultimate 3000 analytical system with a CAD detector. Chromatographic separations were carried out using the Luna C8 column (250 \(\times\) 4.6 mm, 5 \(\upmu\)m). The calibration curve was obtained by the analysis of different concentrations of CLO in PBS solutions (0.05-2.00 mg/mL). The analytical method was validated by the Pharmaceutical Research Institute in Poland.