Compound characterization data — Hertel et al., 2026

Raphael Hertel, Bence Dajka, Pooja Bhat Mulki, Michael Walter, Michael Sommer. “Thermodynamically controlled mechanochromism through dynamic boron–nitrogen bonds.” ChemRxiv (2026). https://doi.org/10.26434/chemrxiv.15008003/v1

The supporting information is appended to the main paper

3-(3-buten-1-yl)-2-methylthiophene
¹H NMR (600.1 MHz, CDCl₃)	δ / ppm 6.99 (d, ³JHH = 5.2 Hz, 1 H, 4-H), 6.82 (d, ³JHH = 5.2 Hz, 1 H, 5-H), 5.85 (ddt, ³JHH = 16.9 Hz, ³JHH = 10.2 Hz, ³JHH = 6.6 Hz, 1 H, –CHCH₂), 5.08–5.01 (m, 1 H, –CHCH₂), 5.00–4.95 (m, 1 H, –CHCH₂), 2.64–2.57 (m, 2 H, –CH₂CH₂CHCH₂), 2.36 (s, 3 H, –CH₃), 2.33–2.26 (m, 2 H, –CH₂CH₂CHCH₂)
¹³C{¹H} NMR (150.9 MHz, CDCl₃)	δ / ppm 138.3 (–CHCH₂), 137.4 (C2), 132.9 (C3), 128.9 (C5), 121.0 (C4), 115.1 (–CHCH₂), 34.7 (–CH₂CH₂CHCH₂), 27.9 (–CH₂CH₂CHCH₂), 13.1 (–CH₃)
GC–MS (EI)	tᵣ 15.23 min; m/z [ion] (% relative intensity): 111.0 [M−C₃H₅]⁺ (100), 152.1 [M]⁺ (40)
¹H and ¹³C{¹H} NMR spectra	Image data were not transcribed

4,7-dibromo-2-(hex-5-en-1-yl)-2H-benzo[d][1,2,3]triazole
Identifier	S1
¹H NMR (600.1 MHz, CDCl₃)	δ / ppm 7.44 (s, 2 H, 5-H, 6-H), 5.77 (ddt, ³JHH = 17.0 Hz, ³JHH = 10.2 Hz, ³JHH = 6.7 Hz, 1 H, –CHCH₂), 5.07–5.00 (m, 1 H, –CHCH₂), 4.99–4.95 (m, 1 H, –CHCH₂), 4.79 (t, ³JHH = 7.4 Hz, 2 H, –CH₂(CH₂)₃CHCH₂), 2.22–2.04 (m, 4 H, –CH₂CH₂CH₂CH₂CHCH₂), 1.49 (p, ³JHH = 7.5 Hz, 2 H, –(CH₂)₂CH₂CH₂CHCH₂)
¹³C{¹H} NMR (150.9 MHz, CDCl₃)	δ / ppm 143.9 (C3a, C7a), 137.9 (–CHCH₂), 129.7 (C5, C6), 115.4 (–CHCH₂), 110.1 (C4, C7), 57.4 (–CH₂(CH₂)₃CHCH₂), 33.2 (–CH₂CHCH₂), 29.8 (–CH₂CH₂(CH₂)₂CHCH₂), 25.9 (–(CH₂)₂CH₂CH₂CHCH₂)
HRMS (APCI)	m/z calcd for C₁₂H₁₃Br₂N₃: 357.9549 [M+H]⁺, found: 357.9559
¹H and ¹³C{¹H} NMR spectra	Image data were not transcribed

4,7-di(4-(but-3-en-1-yl)-5-methyl-2-thienyl)-2-(hex-5-en-1-yl)-2H-benzo[d][1,2,3]triazole
Identifier	S2
¹H NMR (600.1 MHz, CDCl₃)	δ / ppm 7.79 (s, 2 H, 3′-H), 7.48 (s, 2 H, 5-H, 6-H), 5.92 (ddt, ³JHH = 16.9 Hz, ³JHH = 10.2 Hz, ³JHH = 6.6 Hz, 2 H, –C(CH₂)₂CHCH₂), 5.81 (ddt, ³JHH = 16.9 Hz, ³JHH = 10.2 Hz, ³JHH = 6.7 Hz, 1 H, –N(CH₂)₄CHCH₂), 5.13–4.95 (m, 6 H, –CHCH₂), 4.83 (t, ³JHH = 7.2 Hz, 2 H, –NCH₂(CH₂)₃CHCH₂), 2.80–2.58 (m, 4 H, –CCH₂CH₂CHCH₂), 2.42 (s, 6 H, –CH₃), 2.42–2.37 (m, 4 H, –CCH₂CH₂CHCH₂), 2.26–2.12 (m, 4 H, –NCH₂CH₂CH₂CH₂CHCH₂), 1.62–1.55 (m, 2 H, –N(CH₂)₂CH₂CH₂CHCH₂)
¹³C{¹H} NMR (150.9 MHz, CDCl₃)	δ / ppm 142.2 (C3a, C7a), 138.7 (C4′), 138.4 (–C(CH₂)₂CHCH₂), 138.3 (–N(CH₂)₄CHCH₂), 135.5 (C2′), 133.9 (C5′), 128.8 (C3′), 123.3 (C4, C7), 122.2 (C5, C6), 115.2 (–N(CH₂)₄CHCH₂), 115.1 (–C(CH₂)₂CHCH₂), 56.6 (–NCH₂(CH₂)₃CHCH₂), 34.7 (–CCH₂CH₂CHCH₂), 33.3 (–N(CH₂)₃CH₂CHCH₂), 29.6 (–NCH₂CH₂(CH₂)₂CHCH₂), 28.1 (–CCH₂CH₂CHCH₂), 26.0 (–N(CH₂)₂CH₂CH₂CHCH₂), 13.3 (–CH₃)
HRMS (ESI)	m/z calcd for C₃₀H₃₅N₃S₂⁺: 501.2267 M⁺, found: 501.2267
¹H and ¹³C{¹H} NMR spectra	Image data were not transcribed

4,7-di(4-(4-(4-bromophenyl)butyl)-5-methyl-2-thienyl)-2-(6-(4-bromophenyl)hexyl)-2H-benzo[d][1,2,3]triazole
Identifier	4
¹H NMR (600.1 MHz, CDCl₃)	δ / ppm 7.72 (s, 2 H, 63-H, 83-H), 7.48 (s, 2 H, 75-H, 76-H), 7.37 (d, ³JHH = 8.0 Hz, 4 H, 13-H, 133-H), 7.34 (d, ³JHH = 8.0 Hz, 2 H, –(CH₂)₆CCHCHCBr), 7.05 (d, ³JHH = 8.0 Hz, 4 H, 12-H, 132-H), 6.99 (d, ³JHH = 8.0 Hz, 2 H, –(CH₂)₆CCHCHCBr), 4.79 (t, ³JHH = 7.0 Hz, 2 H, –NCH₂(CH₂)₅C₆H₄Br), 2.64–2.56 (m, 8 H, 2-H, 5-H, 9-H, 12-H), 2.53 (t, ³JHH = 7.7 Hz, 2 H, –N(CH₂)₅CH₂C₆H₄Br), 2.40 (s, 6 H, –CH₃), 2.20–2.13 (m, 2 H, –NCH₂CH₂(CH₂)₄C₆H₄Br), 1.71–1.63 (m, 8 H, 3-H, 4-H, 10-H, 11-H), 1.62–1.56 (m, 2 H, –N(CH₂)₄CH₂CH₂C₆H₄Br), 1.48–1.37 (m, 4 H, –N(CH₂)₂(CH₂)₂(CH₂)₂C₆H₄Br)
¹H NMR (600.1 MHz, C₆D₆)	δ / ppm 8.16 (s, 2 H, 63-H, 83-H), 7.59 (s, 2 H, 75-H, 76-H), 7.27–7.24 (m, 6 H, 13-H, 133-H, –(CH₂)₆CCHCHCBr), 6.66 (d, ³JHH = 8.2 Hz, 4 H, 12-H, 132-H), 6.62 (d, ³JHH = 8.2 Hz, 2 H, –(CH₂)₆CCHCHCBr), 4.38 (t, ³JHH = 7.0 Hz, 2 H, –NCH₂(CH₂)₅C₆H₄Br), 2.41 (t, ³JHH = 7.4 Hz, 4 H, 2-H, 12-H), 2.25 (t, ³JHH = 7.4 Hz, 4 H, 5-H, 9-H), 2.17 (s, 6 H, –CH₃), 2.16–2.11 (m, 2 H, –N(CH₂)₅CH₂C₆H₄Br), 1.82–1.75 (m, 2 H, –NCH₂CH₂(CH₂)₄C₆H₄Br), 1.53–1.39 (m, 8 H, 3-H, 4-H, 10-H, 11-H), 1.21–1.16 (m, 2 H, –N(CH₂)₄CH₂CH₂C₆H₄Br), 1.03–0.90 (m, 4 H, –N(CH₂)₂(CH₂)₂(CH₂)₂C₆H₄Br)
¹³C{¹H} NMR (150.9 MHz, CDCl₃)	δ / ppm 142.0 (C73a, C77a), 141.5 (C11, C131), 141.4 (–(CH₂)₆CCHCHCBr), 139.0 (C64, C84), 135.3 (C62, C82), 133.6 (C65, C85), 131.3 (C13, C133), 131.3 (–(CH₂)₆CCHCHCBr), 130.2 (C12, C132), 130.1 (–(CH₂)₆CCHCHCBr), 128.6 (C63, C83), 123.2 (C74, C77), 122.1 (C75, C76), 119.4 (C14, C134), 119.4 (–(CH₂)₆CCHCHCBr), 56.6 (–NCH₂(CH₂)₅C₆H₄Br), 35.2 (C2, C12), 35.2 (–N(CH₂)₅CH₂C₆H₄Br), 31.0 (–N(CH₂)₄CH₂CH₂C₆H₄Br), 30.9 (C3, C11), 30.0 (C4, C10), 29.9 (–NCH₂CH₂(CH₂)₄C₆H₄Br), 28.5 (–N(CH₂)₂CH₂(CH₂)₃C₆H₄Br), 28.2 (C5, C9), 26.4 (–N(CH₂)₃CH₂(CH₂)₂C₆H₄Br), 13.2 (–CH₃)
HRMS (ESI)	m/z calcd for C₄₈H₅₀Br₃N₃S₂: 969.0991 M⁺, found: 969.0993
HRMS (APCI)	m/z calcd for C₄₈H₅₀Br₃N₃S₂: 970.1075 [M+H]⁺, found: 970.1117
¹H and ¹³C{¹H} NMR spectra	Image data were not transcribed

2-(6-bromo-1-hexyl)-4-(3-B,B-diethylboryl-5-methyl-2-thienyl)-7-(5-methyl-2-thienyl)-2H-benzo[d][1,2,3]triazole
Identifier	Et2B-1
UV–vis absorption in DCM solution (10 µmol L⁻¹)	Bathochromic shift of 61 nm compared to non-borylated 1
Photoluminescence in DCM solution (10 µmol L⁻¹)	Bathochromic shift of 120 nm compared to non-borylated 1
UV–vis absorption and photoluminescence in DCM solution (10 µmol L⁻¹)	The large Stokes shift allowed simultaneous detection of the photoluminescence of the boracyclic closed and open N–B forms without overlap of excitation and emission
UV–vis absorption and ¹¹B NMR in solution	Predominantly in the closed boracyclic form; not significantly altered by different excitation wavelengths
¹H NMR (600.1 MHz, CDCl₃)	δ / ppm 7.76 (d, ³JHH = 3.6 Hz, 1 H, 3′′-H), 7.53 (d, ³JHH = 7.5 Hz, 1 H, 6-H), 7.21 (d, ³JHH = 7.5 Hz, 1 H, 5-H), 6.83 (d, ³JHH = 3.5 Hz, 1 H, 4′′-H), 6.70 (bs, 1 H, 4′-H), 4.95 (t, ³JHH = 7.5 Hz, 2 H, –NCH₂(CH₂)₅Br), 3.44 (t, ³JHH = 6.7 Hz, 2 H, –N(CH₂)₅CH₂Br), 2.56 (s, 3 H, –C5′′CH₃), 2.55 (s, 3 H, –C5′CH₃), 2.26 (p, ³JHH = 7.4 Hz, 2 H, –NCH₂CH₂(CH₂)₄Br), 1.93 (p, ³JHH = 6.8 Hz, 2 H, –N(CH₂)₄CH₂CH₂Br), 1.65–1.56 (m, 4 H, –N(CH₂)₂(CH₂)₂(CH₂)₂Br), 0.90–0.76 (m, 4 H, –BCH₂CH₃), 0.37 (t, ³JHH = 7.6 Hz, 6 H, –BCH₂CH₃)
¹¹B NMR (80.5 MHz, CDCl₃)	δ / ppm 3.9
¹³C{¹H} NMR (150.9 MHz, CDCl₃)	δ / ppm 163.0 (C3′), 141.4 (C5′), 140.4 (C5′′), 139.9 (C7a), 137.6 (C3a), 137.0 (C2′′), 131.0 (C4′), 130.5 (C2′), 126.6 (C4′′), 126.5 (C3′′), 125.2 (C6), 124.7 (C4), 120.8 (C7), 118.3 (C5), 55.1 (–NCH₂(CH₂)₅Br), 33.6 (–N(CH₂)₅CH₂Br), 32.6 (–N(CH₂)₄CH₂CH₂Br), 29.6 (–NCH₂CH₂(CH₂)₄Br), 27.8 (–N(CH₂)₃CH₂(CH₂)₂Br), 26.0 (–N(CH₂)₂CH₂(CH₂)₃Br), 17.9 (–BCH₂), 15.9 (–C5′′CH₃), 15.7 (–C5′CH₃), 10.6 (–BCH₂CH₃)
HRMS (APCI)	m/z calcd for C₂₆H₃₃BBrN₃S₂: 542.1470 [M+H]⁺, found: 542.1489
MALDI-TOF	m/z [ion] (% relative intensity): 514.2 [M−C₂H₄+H]⁺ (100); 542.3 [M+H]⁺ (4)
¹H and ¹³C{¹H} NMR spectra	Image data were not transcribed
¹¹B NMR spectrum with baseline suppression (acetone-d₆)	Image data were not transcribed

4-(4-(4-(4-bromophenyl)butyl)-3-(B-ethyl-B-phenylboryl)-5-methyl-2-thienyl)-7-(4-(4-(4-bromophenyl)butyl)-5-methyl-2-thienyl)-2-(6-(4-bromophenyl)hexyl)-2H-benzo[d][1,2,3]triazole
Identifier	EtPhB-4
Photoluminescence in dichloromethane solution	Following excitation at 370 nm, the spectra exhibited an increased contribution of the open form compared to excitation ≤360 nm and ≥400 nm
Photoluminescence spectra and I₄₆₈/I₆₀₀ ratio at different excitation wavelengths in DCM solution (10 µmol L⁻¹)	Image data were not transcribed
¹H NMR (600.1 MHz, acetone-d₆)	δ / ppm 7.77 (s, 1 H, 83-H), 7.68 (d, ³JHH = 7.5 Hz, 1 H, 76-H), 7.46–7.37 (m, 7 H, 13-H, 75-H, 133-H, –(CH₂)₆CCHCHCBr), 7.35 (d, ³JHH = 7.3 Hz, 2 H, –BCCH), 7.20 (t, ³JHH = 7.3 Hz, 2 H, –BCCHCH), 7.16–7.11 (m, 3 H, 12-H, –BCCHCHCH), 7.12–7.07 (m, 4 H, 132-H, –(CH₂)₆CCHCHCBr), 4.69–4.55 (m, 2 H, –NCH₂(CH₂)₅Br), 2.69–2.57 (m, 4 H, 9-H, 12-H), 2.50 (t, ³JHH = 7.7 Hz, 2 H, –N(CH₂)₅CH₂C₆H₄Br), 2.41 (s, 3 H, –85CH₃), 2.39–2.24 (m, 7 H, 2-H, 5-H, –65CH₃), 1.77–1.62 (m, 6 H, 10-H, 11-H, –N(CH₂)₄CH₂CH₂C₆H₄Br), 1.51–1.42 (m, 4 H, 3-H, 4-H), 1.41–1.32 (m, 2 H, –BCH₂CH₃), 1.14–0.97 (m, 6 H, –NCH₂(CH₂)₃(CH₂)₂C₆H₄Br), 0.24 (t, ³JHH = 7.5 Hz, 3 H, –BCH₂CH₃)
¹¹B NMR (80.5 MHz, CDCl₃)	δ / ppm 1.0
¹³C{¹H} NMR (150.9 MHz, acetone-d₆)	δ / ppm 160.2 (C63), 151.5 (–BCCH), 144.5 (C65), 143.1 (C131), 142.8 (–(CH₂)₆CCHCHCBr), 142.7 (C11), 140.4 (C85), 139.9 (C77a), 137.1 (C73a), 136.3 (C64), 134.9 (C82), 134.7 (C84), 134.4 (–BCCH), 132.1 (C133), 132.0 (–(CH₂)₆CCHCHCBr), 132.0 (C13), 131.4 (C12), 131.3 (–(CH₂)₆CCHCHCBr), 131.3 (C132), 129.6 (C83), 129.1 (C62) 128.5 (–BCCHCH), 126.8 (–BCCHCHCH), 125.6 (C76), 124.5 (C74), 121.8 (C77), 119.8 (C134), 119.8 (–(CH₂)₆CCHCHCBr), 119.6 (C14), 119.3 (C75), 56.2 (–NCH₂(CH₂)₅C₆H₄Br), 35.8 (C2), 35.6 (C12), 35.5 (–N(CH₂)₃CH₂(CH₂)₂C₆H₄Br), 32.8 (–N(CH₂)₃CH₂(CH₂)₂C₆H₄Br), 31.6 (C11), 31.6 (C3), 30.4 (–N(CH₂)₄CH₂CH₂C₆H₄Br), 30.1 (C10), 29.7 (C5), 29.1 (C5), 29.0 (–N(CH₂)₂CH₂(CH₂)₃C₆H₄Br), 28.5 (C9), 26.6 (–NCH₂CH₂(CH₂)₄C₆H₄Br), 15.0 (–BCH₂CH₃), 13.6 (–C65CH₃), 13.1 (–C85CH₃), 10.2 (–BCH₂CH₃)
HRMS (ESI)	m/z calcd for C₅₆H₅₉BBr₃N₃S₂: 1085.1794 M⁺, found: 1085.1807
MALDI-TOF	m/z [ion] (% relative intensity): 1060.3 [M−C₂H₄+H]⁺ (100); 1088.3 [M+H]⁺ (2)
¹H and ¹³C{¹H} NMR spectra (acetone-d₆)	Image data were not transcribed
¹¹B NMR spectrum with baseline suppression (acetone-d₆)	Image data were not transcribed

Chromophore-functionalized poly(meta,meta,para)phenylene
Identifier	3
SEC, number-average molecular weight	29 kg mol⁻¹
SEC, weight-average molecular weight	159 kg mol⁻¹
Photoluminescence during uniaxial tensile testing (100 µm film)	Peak at 482 nm; no response upon tensile testing
Photoluminescence spectra, emission wavelength and optical image during tensile testing	Image data were not transcribed
¹H NMR (600.1 MHz, C₆D₆)	δ / ppm 8.23 (s, –SCCH), 7.93 (d, ⁴JHH = 2.4 Hz, 2 H, 2-H), 7.71 (s, 2 H, 2′-H), 7.63 (dd, ³JHH = 8.5 Hz, ⁴JHH = 2.4 Hz, 2 H, 6-H), 6.92 (d, ³JHH = 8.5 Hz, 2 H, 5-H), 4.40 (–NCH₂), 4.24 (–NCH₂) 3.77 (t, ³JHH = 6.4 Hz, 4 H, 7-H), 2.60–2.33 (m, Ar–CH₂), 2.20 (s, –SCCH₃), 2.14–2.04 (m, –SCCH₃, Ar–CH₂), 1.72–1.41 (m, 4 H, 8-H), 1.29–1.03 (m, 12 H, 9-H, 10-H, 11-H), 0.83 (t, ³JHH = 7.2 Hz, 6 H, 12-H)
¹H NMR spectrum (C₆D₆)	Image data were not transcribed
¹H NMR spectrum after treatment with 0.5 eq BCl₃ in DCM (CDCl₃)	Image data were not transcribed
¹H NMR spectrum after treatment with 2 eq BCl₃ in DCM (THF-d₈)	Image data were not transcribed

Ethyl-substituted borylated polymer
Identifier	EtB-3
Photoluminescence of films at 370 and 400 nm excitation	Nearly identical emission spectra
Photoluminescence spectra of films at different excitation wavelengths	Image data were not transcribed
Photoluminescence of solutions at different excitation wavelengths	Only spectra recorded with 450 nm excitation contained B–N bonded state emission
¹¹B NMR of solutions in the dark	A single resonance corresponding to tetracoordinated boron, indicating B–N bonded species
¹H NMR (600.1 MHz, C₆D₆)	δ / ppm 8.14 (s, –SCCH), 8.10–7.40 (m, 8 H, 2-H, 6-H, 2′-H), 6.91 (d, ³JHH = 7.9 Hz, 2 H, 5-H), 3.91–3.70 (m, 4 H, 7-H), 1.73–1.40 (m, 4 H, 8-H), 1.37–0.99 (m, 12 H, 9-H, 10-H, 11-H), 0.94–0.67 (m, 6 H, 12-H), 0.20 (m, –BCH₂CH₃)
¹¹B NMR (80.5 MHz, C₆D₆)	δ / ppm −1
¹H and ¹¹B NMR spectra (C₆D₆)	Image data were not transcribed

Mesityl-substituted borylated polymer
Identifier	MesB-3
¹H NMR (600.1 MHz, C₆D₆)	δ / ppm 8.15 (s, bs, –SCCH), 7.99–7.87 (m, 2 H, 2-H), 7.75–7.57 (m, 6 H, 6-H, 2′-H), 6.92 (d, ³JHH = 8.4 Hz, 2 H, 5-H), 6.70 (s, Mes–H), 6.67 (s, Mes–H), 4.55 (bs, –NCH₂), 4.28 (bs, –NCH₂), 3.77 (t, ³JHH = 6.0 Hz, 4 H, 7-H), 2.98 (bs, SCCCH₂), 2.78 (bs, SCCCH₂), 2.65–2.40 (m, Ar–CH₂), 2.24 (s, Mes–CH₃), 2.16 (s, –SCCH₃), 2.14 (s, Mes–CH₃), 2.06 (s, Mes–CH₃), 1.96 (s, –SCCH₃), 1.60–1.45 (m, 4 H, 8-H), 1.30–1.03 (m, 12 H, 9-H, 10-H, 11-H), 0.89–0.75 (m, 6 H, 12-H)
¹¹B NMR (80.5 MHz, C₆D₆)	δ / ppm −1
¹H and ¹¹B NMR spectra (C₆D₆)	Image data were not transcribed

2,4,6-tri-tert-butylphenyl-substituted borylated polymer
Identifier	Mes*B-3
¹H NMR (600.1 MHz, C₆D₆)	δ / ppm 8.15 (s, bs, –SCCH), 7.93 (d, ⁴JHH = 2.2 Hz, 2 H, 2-H), 7.71 (s, 4 H, 2′-H), 7.63 (dd, ⁴JHH = 8.4 Hz, ⁴JHH = 2.1 Hz, 2 H, 6-H), 7.43 (s, –CHCt-Bu), 6.92 (d, ³JHH = 8.5 Hz, 2 H, 5-H), 4.75 (bs, –NCH₂), 4.54 (bs, –NCH₂), 3.77 (t, ³JHH = 6.3 Hz, 4 H, 7-H), 2.70–2.39 (m, Ar–CH₂), 2.29–2.13 (m, –SCCH₃, Ar–CH₂), 1.73–1.40 (m, 4 H, 8-H), 1.35 (s, –C(CH₃)₃), 1.30–1.03 (m, 12 H, 9-H, 10-H, 11-H), 0.94–0.67 (m, 6 H, 12-H)
¹¹B NMR (80.5 MHz, C₆D₆)	δ / ppm −2
¹H and ¹¹B NMR spectra (C₆D₆)	Image data were not transcribed
Photoluminescence wavelength during solvent-vapor exposure and emission images in dichloromethane, as a neat thin film, and after dichloromethane-vapor annealing	Image data were not transcribed
Photoluminescence wavelength after solvent-vapor annealing with cyclohexane, diethyl ether, methanol, or acetonitrile	Not significantly affected
Photoluminescence after exposure to polymer-solubilizing solvent vapors	Photoluminescence intensity resulting from the closed, boracyclic state was reduced
Photoluminescence wavelength after exposure to toluene, THF, or dichloromethane vapor	Converged to approximately 525 nm for all solvents
Temperature-dependent photoluminescence spectra, wavelength and optical images after sample failure and for thermally equilibrated films	Image data were not transcribed
Time-resolved photoluminescence spectra during exposure to cyclohexane, diethyl ether, acetonitrile, methanol, THF, toluene and DCM vapors (370 nm excitation)	Image data were not transcribed

EtB-3, MesB-3 and Mes*B-3 films
SEC, molecular-weight distribution	Not affected by the polymer-analogous borylation/transmetalation sequence
NMR, repeat-unit chemical shifts	Not affected by the polymer-analogous borylation/transmetalation sequence
Photoluminescence under UV excitation before and after dissolution	Emission changed from orange to turquoise upon dissolution; solution spectra excited at 370 nm were indistinguishable from those of non-borylated polymer 3
Photoluminescence during uniaxial tensile testing (100 µm films)	A new band at 563 nm arose; its intensity and wavelength continuously decreased upon straining
Photoluminescence emission wavelength during uniaxial tensile testing	At 0 %–50 % strain, the wavelength remained constant until strain-induced necking reached the detected area; at 50 %–150 % strain, the wavelength decreased to a constant value; at >150 % strain, the hypsochromic shift continued
Photoluminescence blueshift during uniaxial tensile testing	EtB-3: 16 nm; MesB-3: 24 nm; Mes*B-3: 38 nm
Photoluminescence after sample failure (~250 %–300 % strain)	The wavelength relaxed back to the value during necking
Photoluminescence after heating above Tg (120 °C)	The hypsochromic shift was reversed
Photoluminescence of a thermally equilibrated film at 150 °C	Significant changes were not observed
Photoluminescence and visual appearance during uniaxial tensile testing (100 µm films)	EtB-3: orange; MesB-3: yellow; Mes*B-3: turquoise
Photoluminescence spectra, mean wavelength and emission images during tensile testing	Image data were not transcribed

Borylated and non-borylated model compounds
Identifiers	Et2B-1 and 1
UV–vis difference spectrum	Negative signals at 325 nm and 460 nm and a positive signal at 380 nm, reflecting B–N bonded and cleaved form absorption, respectively
UV–vis difference-spectrum plot	Image data were not transcribed
Photoswitching plots	Image data were not transcribed

Borylated and non-borylated polymers
Identifiers	3, EtB-3, MesB-3 and Mes*B-3
Photoluminescence spectra in DCM solution (0.5 mg mL⁻¹) and as thin films (370 nm excitation)	Image data were not transcribed
SEC chromatograms in THF solution before and after polymer-analogous borylation	Image data were not transcribed

Borylated polymer and monomeric model compound
Identifiers	EtB-3 and EtPhB-4
UV–vis spectra in DCM solution (EtB-3: 1 mg mL⁻¹; EtPhB-4: 10 µmol L⁻¹)	Image data were not transcribed

Non-borylated model compound, borylated model compounds and borylated polymer
Identifiers	1, Et2B-1, EtPhB-4 and EtB-3
Photoluminescence spectra in DCM solution at 370, 405 and 450 nm excitation (model compounds: 10 µmol L⁻¹; polymer: 1 mg mL⁻¹)	Image data were not transcribed