## 1 Introduction
The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution (Mw/Mn) were determined by size-exclusion chromatography using a Shimadzu LC-20 Prominence system (Shimadzu Corporation, Kyoto, Japan), equipped with a differential refractive index detector Shimadzu RID-20A at 50 \({}^{\circ}\)C. The column was Agilent PolyPore 7.5 \(\times\) 300 mm (PL1113-6500) with a guard column. The system was operated at the flow rate of 0.7 mL/min using DMF containing 0.05M LiBr as the eluent. A set of 12 polystyrene standards (Polystyrene High EasiVials PL2010-0201, Agilent, Santa Clara, CA, USA) ranging from 162 to 6,570,000 g/mol was employed for calibration. STA 449 Jupiter (Netzsch, Selb, Germany) was used to perform the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) in the air at a heating rate of 5 \({}^{\circ}\)C/min from 20 to 800 \({}^{\circ}\)C. The copolymers had an electrical conductivity of 10\({}^{-13}\) S/cm; after doping with iodine for 48 h, the electrical conductivity increased by four orders of magnitude (10\({}^{-9}\) S/cm). Metal\(-\)polymer complexes of the synthesized VT-VK polymer ligands and Tb\({}^{3+}\) ions were prepared in DMF. Films of the studied MPC in a poly(methyl methacrylate) (PMMA) matrix were obtained as follows. To solutions containing 50 mg of PMMA in DMF, the previously prepared solutions of the obtained MPC were added to a total volume of 2 mL. The polymer concentration depended on the content of VK units, as the concentration of the latter was brought up to 10\({}^{-3}\) M in all cases. The [Tb\({}^{3+}\)]-[VK] ratio was 1:1. The complex was obtained from the solution using the salt TbCl\({}_{3}\) x 6H\({}_{2}\)O. The finally prepared solution was poured onto a glass substrate into rings with an area of 4 cm\({}^{2}\) and dried at 60 \({}^{\circ}\)C to a constant weight. The mass concentration of Tb\({}^{3+}\) ions (\(\sim\)0.63%) and VK units (\(\sim\)0.77%) in the resulting films was constant, which is necessary for a correct comparison of the luminescence intensities for MPC based on copolymers of different compositions. Absorption spectra of poly(VT-co-VK) solutions were recorded on a spectrophotometer SF-256 UVI (LOMO, St. Petersburg, Russia) in the range from 250 to 450 nm. The polymer concentration in DMF was chosen in the range from 0.1 to 1 mg/mL. The photoluminescence spectra of both the synthesized VT-VK copolymers and their metal-polymer complexes with Tb\({}^{3+}\) ions were recorded on an LS-100 BASE luminescence spectrophotometer (PTI\({}^{\circledR}\) Lasers INC, London-Toronto, ON, Canada) equipped with a solid sample holder for polymer films. The luminescent signal was measured from the side of the incidence of the exciting beam. The spectral width of the slits at the input and output of the observation and excitation monochromators was 4 nm. Luminescence excitation at 300 nm was used. Photoluminescence in the fluorescent mode was observed in the range of 320-700 nm, covering almost the entire visible range. The magnitude of the luminescence intensity was numerically reduced to a single PMT gain, taking into account the laboratory standard. Such a reduction in the measured luminescence signal made it possible to compare the relative intensity for different conditions, taking into account the fact that in this work, the concentration of Tb\({}^{3+}\) ions and VK units was maintained constantly.