## 4 Conclusions  
The development of pyrrolinium-based polymeric ionic liquids for solid phase microextraction fibers is here presented for the first time. Three different polymers with different alkyl side chain lengths of two, eight, and fourteen carbons were synthesized and used as dense SPME fibers. A one step, solvent free, simple, and time saving polymerization and fiber preparation strategy, through the use of UV irradiation, was successfully demonstrated. The results obtained for a model mixture of analytes from different chemical families indicate that the PIL-based fibers are well suited for the model solution, being the polymer with longer alkyl chain length the better performing one, in terms of detection capability, due to its larger free volume. A comparison with the commercially available fibers based on Polyacrylate and Polydimethylsiloxane allows us to conclude that the PIL-based fibers displayed a superior performance. Good recoveries were obtained when studying a urine sample, ranging from 60.2% to 104.1%. Therefore, further research on poly(ionic liquid) materials for development of analytical tools that allow for the detection of very low concentration of diverse compounds is of great interest. The inherent tunability of this class of materials will be very valuable in the detection of specific families of compounds.  
The following are available online at www.mdpi.com/1996-1944/10/9/1094/s1, Figure S1: \({}^{1}\)H-NMR data example of the synthesized diallymethyloctyl bromide ([DAMC\({}_{8}\)] Br) ionic liquid monomer.; Figure S2: Thermo gravimetric analysis data of the crosslinked poly(methyloctyl pyrrolinium) TFSI (pD8) under N\({}_{2}\) atmosphere.; Figure S3: Thermo gravimetric analysis data of the crosslinked poly(methylethyl pyrrolinium) TFSI (pD2) under N\({}_{2}\) atmosphere.; Figure S4: Differential Scanning Calorimetry data of the crosslinked poly(methylretadecyl pyrrolinium) TFSI (pD14).; Figure S5: Differential Scanning Calorimetry data of the crosslinked polymers. From top to bottom: pD14, pD8 and pD2.; Table S1: Glass transition temperatures and decomposition temperatures obtained for the three crosslinked polymers. Table S2: Representation of the linear range and limits of detection for the analytes under study for the pD14 fiber. (\(T\) = 45 \({}^{\circ}\)C, \(t\) = 15 min, 2.5 wt % of NaCl, 200 rpm).  
**Acknowledgments:** [PERSON], and [PERSON] are grateful to FCT (_Fundacao para a Ciencia e a Tecnologia_) for the PhD research grant SFR/BD/97042/2013 and the Post-Doctoral research grant (SFRH/BPD/101793/2014), respectively. [PERSON] also thanks the financial support from COST-Exil Project 1206. The NMR data was acquired at CERMAX (Centro de Resonancia Magnetica Antonio Xavier) which is a member of the National NMR network. This work was partially supported by FCT through Research Unit GREEN-it \"Bioresources for Sustainability\" (UID/Multi/04551/2013) and the Associate Laboratory CICECO Aveiro Institute of materials (UID/CTM/50011/2013).  
**Author Contributions:** [PERSON], [PERSON] and [PERSON] were actively working on practical synthesis, chromatographic analysis, thermal analysis, N.M.R. and writing process. [PERSON], [PERSON] and [PERSON] are experts in polymers, poly (ionic liquids), analytical chemistry, ionic liquids and were actively working on design, ideas and writing process.  
**Conflicts of Interest:** The authors declare no conflict of interest.