Visualizing Chain Growth of Polytelluoxane via Polymerization Induced Emission

Abstract Visualizing polymer chain growth is always a hot topic for tailoring structure‐function properties in polymer chemistry. However, current characterization methods are limited in their ability to differentiate the degree of polymerization in real‐time without isolating the samples from the reaction vessel, let alone to detect insoluble polymers. Herein, a reliable relationship is established between polymer chain growth and fluorescence properties through polymerization induced emission. (TPE‐C2)2‐Te is used to realize in situ oxidative polymerization, leading to the aggregation of fluorophores. The relationship between polymerization degree of growing polytelluoxane (PTeO) and fluorescence intensity is constructed, enabling real‐time monitoring of the polymerization reaction. More importantly, this novel method can be further applied to the observation of the polymerization process for growing insoluble polymer via surface polymerization. Therefore, the development of visualization technology will open a new avenue for visualizing polymer chain growth in real‐time, regardless of polymer solubility.

H NMR and 13 C NMR spectra were obtained from BRUKER ASCENDTM 400 spectrometer.The GPC measurements were performed by Waters 515 (Milford, MA) (standard: polystyrene, eluent: THF).Electrospray Ionization Mass Spectrometry were acquired with TOF-Q Ⅱ 10280 (Varian Inc., USA).Ultraviolet visible (UV-vis) spectra were recorded on a UV-2450-visible spectrophotometer (Shimadzu, Japan).The X-ray photoelectron spectroscopy (XPS) was employed by a PHI Quantera scanning X-ray microprobe.The Time of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was performed on a ION-TOF GmbH TOF-SIMS.

Synthesis of (TPE-C2)2-Te
A total tellurium powder (0.06g, 0.46 mmol) and sodium borohydride (0.044g, 1.2 mmol) were added to 5 mL of water under the atmosphere of nitrogen.After 30 min of stirring under at 50 °C, TPE-C2-Br (0.12 g, 0.27 mmol) dissolved in THF (5 mL) was added.The reaction was stirred at 50 °C for 12 h.Then solvent was removed under vacuum, the residue re-dissolved in CH2Cl2 (30 mL).The combined organic phase was concentrated and purified by flash column chromatography to afford compound (TPE-C2)2-Te as yellow solid (0.032 g).

Synthesis of (TPE-C6)2-Te
A total tellurium powder (0.06g, 0.46 mmol) and sodium borohydride (0.044g, 1.2 mmol) were added to 5 mL of water under the atmosphere of nitrogen.After 30 min of stirring under at 50 °C, TPE-C6-Br (0.13 g, 0.25 mmol) dissolved in THF (5 mL) was added.The reaction was stirred at 50 °C for 12 h.Then solvent was removed under vacuum, the residue re-dissolved in CH2Cl2 (30 mL).The combined organic phase was concentrated and purified by flash column chromatography to afford compound (TPE-C6)2-Te as yellow solid (0.042 g).

Synthesis of (TPE-C12)2-Te
A total tellurium powder (0.06g, 0.46 mmol) and sodium borohydride (0.044g, 1.2 mmol) were added to 5 mL of water under the atmosphere of nitrogen.After 30 min of stirring under at 50 °C, TPE-C12-Br (0.16 g, 0.27 mmol) dissolved in THF (5 mL) was added.The reaction was stirred at 50 °C for 12 h.Then solvent was removed under vacuum, the residue re-dissolved in CH2Cl2 (30 mL).The combined organic phase was concentrated and purified by flash column chromatography to afford compound (TPE-C12)2-Te as yellow solid (0.02 g).

Results and discussion
Figure S7.The formula of oxidation polymerization.
A total tellurium powder (0.03g, 0.23 mmol) and sodium borohydride (0.022g, 0.6 mmol) were added to 5 mL of water under the atmosphere of nitrogen.After 30 min of stirring under at 45 °C, 5-Bromovaleric acid (0.02 g, 0.12 mmol) dissolved in THF (5 mL) was added.The reaction was stirred at 45 °C for 12 h.Then solvent was removed under vacuum, the residue re-dissolved in CH2Cl2 (30 mL).Products were purified by filtration and recrystallization.According to our previous work, [2] the quartz substrate was first modified with 3aminopropyltriethoxysilane in toluene by a silylation reaction.Then, the modified surface with amino groups was then treated with (HOOCC4)2Te to obtain the tellurium-containing quartz surface denoted as SiO2-NHCOTe.For a standard surface modification process, 0.2 mol/L (HOOCC4)2Te was dissolved in chloroform and was then covered on the SiO2-NH2 surface.The obtained surface was washed with acetone and dried by N2 flow.To confirm the successful modification of amino functional groups, a static water contact angle (WAC) experiment was first conducted.For the unmodified SiO2-NH2 surface, WAC was 38±1℃ (Figure S12a).After silylation reaction, the WAC increased to 53±2℃ as a result of the relatively hydrophobic aliphatic structure.The single peak for N 1s spectra shown in the XPS of SiO2-NH2 surface (Figure S12b), verifying the successful modification of amino functional groups.Then, SiO2-NHCOTe surface was prepared through amidation reaction between SiO2-NH2 and (HOOCC4)2Te.In Figure S12c, the binding energies of Te at 584.2 and 573.9 eV were attributed to Te 3d, verifying the chemical structure of the tellurium.Additionally, we also used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to scan the tellurium surface.It can be seen that for a 200 X 200 μm area, Te was uniformly distributed on the surface (Figure S12d).All these results indicated SiO2-NHCOTe was successfully constructed.

Figure S10 .
Figure S10.Fluorescent spectra of TPE treated with H2O2 at different time points.