Diisopropylamine

Natural graphite flakes were purchased from Nacional de Grafite Ltda company (Minas Gerais, Brazil). Phosphoric acid (H₃PO₄, >99%), sulfuric acid (H₂SO₄, 95–98%), dimethylformamide (DMF), p-phenylenediamine (>99%), dibenzylamine (97%), diisopropylamine (99%) and piperidine (99%) were all purchased from Sigma-Aldrich; potassium permanganate (KMnO₄, 99%) was acquired from Neon Commercial.

All chemicals that were used in the reaction were of analytical grade. The poly(vinylidene difluoride) (HSV 900) in powder form was purchased from MTI chemicals, USA. N,N-dimethylformamide (DMF), diisopropylamine and hydrobromic acid (HBr) were purchased from Sigma Aldrich.

Methyl 4-nitrobenzenesulfonate, diisopropylamine, allyl bromide and butyllithium in hexanes (2.5 M) were purchased from Sigma-Aldrich (Steinheim, Germany). 2-Methyl-2-oxazoline (MeOx) provided by TCI (TCI Europe N.V., Belgium) was dried over KOH for 48 h, distilled over CaH₂ under the reduced pressure and stored under argon. Acetonitrile (J.T. Baker, Netherlands, HPLC grade) and dichloromethane (Lach-Ner, Czech Republic) were distilled over CaH₂ and stored on molecular sieves under argon. Tetrahydrofuran (Centralchem, Slovakia) was distilled from sodium benzophenone ketyl prior to use. Isopropanol (Penta s.r.o., Czech Republic) and chloroform (Lach-Ner, Czech Republic) were used as received. For washing of samples before and after plasma treatment deionized water was used.
Polytetrafluoroethylene (PTFE) sheets with a thickness of 1 mm provided by Goodfellow Cambridge Ltd. were used as a substrate material for the deposition of the poly(2-oxazoline) layer. Before experiments, PTFE sheets were cut into different shapes appropriate for individual measurement techniques (squares with dimensions of 1 × 1 cm², rectangles with dimensions of 1 × 2.5 cm², circular samples with a diameter of 15 mm). Before all experiments, PTFE samples were ultrasonically cleaned in isopropanol and distilled water, in both solvents 2 times for 10 min and then dried in the nitrogen flow.

S3I-1757 (white powder with a molecular weight of 521.6 g/mol, soluble in DMSO) was obtained from Glixx Laboratories (Hopkinton, MA, USA). Methoxy-PEO (average molecular weight of 5000 g/mol), diisopropylamine (99%), benzyl chloroformate (tech 95%), sodium (in kerosin), butyllithium in hexane (2.5 M solution), palladium-coated charcoal, pyrene, and Cremophor^® EL were purchased from Sigma Aldrich (St. Louis, MO, USA). α-benzyl carboxylate ε-caprolactone was prepared by Alberta Research Chemicals Incorporation (Edmonton, AB, Canada). Stannous octoate was purchased from MP Biomedicals Incorporation (Solon, OH, USA). All other chemicals were reagent grade. U266 and SupM2 cells were purchased from American Type Culture Collection (Manassas, VA, USA). RPMI8226 cells are a gift from Dr. Linda Pilarski (Department of Oncology, University of Alberta, Edmonton, AB, Canada). The cells were cultured in RPMI 1460 medium with L-glutamine (Life Technology, Carlsbad, CA, USA), 10% FBS (Life technology) and, 100U/mL penicillin/streptomycin (Sigma Aldrich). All cells were incubated at 37 °C supplied with 5% atmospheric CO₂.