Compound characterization data — Jareczek et al., 2026

Mark J. Jareczek, Bhaskar D. Mondal, Zuhair M. Abouelkheir, Arron C. Deacy, Samuel W. Kaplan, Ian A. Tonks, Aleksandr V. Zhukhovitskiy. “Sidechain-alkyne to backbone-allene editing of polyurethanes in solution and solid state.” ChemRxiv (2026). https://doi.org/10.26434/chemrxiv.15007466/v1

But-3-yn-2-yl butylcarbamate
Identifier	1
¹H NMR (600 MHz, CDCl₃)	δ 5.39 (q, 1H, J = 6.6), 4.85 – 4.44 (b, 1H), 3.17 (m, 2H), 2.43 (m, 1H), 1.47 (m, 2H), 1.33 (m, 2H), 0.90 (t, 3H, J = 7.1)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 155.3, 82.9, 72.7, 60.5, 40.9, 30.1, 21.7, 20.0, 13.8 ppm
HRMS (ESI)	calcd. for ¹²C₉H₁₅¹⁴NO₂Na [M+Na]⁺, m/z = 192.09950; found, 192.09970

(R,S)-buta-1,2-dien-1-yl butylcarbamate
Identifier	1′
¹H NMR (600 MHz, CDCl₃)	δ 7.31 (m, 1H), 5.81 (dq, 1H, J = 7.3, 7.0 Hz), 4.83 – 4.52 (m, 1H), 3.21 (q, 2H, J = 6.7 Hz), 1.79 (dd, 3H, J = 7.1, 2.0 Hz), 1.49 (m, 2H), 1.35 (m, 2H), 0.92 (t, 3H J = 7.7 Hz)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 194.3, 154.1, 111.4, 101.2, 41.0, 32.0, 20.0, 16.3, 13.8 ppm
HRMS (ESI)	calcd. for ¹²C₉H₁₅¹⁴NO₂Na [M+Na]⁺, m/z = 192.0995; found, 192.09964

Protected propargylic alcohol
¹H NMR (600 MHz, CDCl₃)	δ 4.31 (t, 1H, J = 4.8 Hz), 1.71 (m, 2H), 1.01 (t, 1H, J = 7.3 Hz), 0.16 (s, 9H)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 106.7, 89.6, 68.1, 31.0, 9.6, 1.2 ppm

Pent-1-yn-3-yl ethylcarbamate
Identifier	2
¹H NMR (600 MHz, CDCl₃)	δ 5.26 (m, 1H), 4.85 – 4.45 (b, 1H), 3.23 (m, 2H), 2.44 (d, 1H, J = 2.1 Hz), 1.78 (m, 2H), 1.14 (t, 3H, J = 7.1 Hz), 1.03 (t, 3H, J = 7.1 Hz)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 155.0, 81.6, 73.3, 65.3, 35.7, 28.1, 15.1, 9.2 ppm
HRMS (ESI)	calcd. for C₈H₁₃NO₂Na [M+Na]⁺, m/z = 178.08385; found, 178.08412

(R,S)-penta-1,2-dien-1-yl ethylcarbamate
Identifier	2′
¹H NMR (600 MHz, CDCl₃)	δ 7.37 (m, 1H), 5.90 (q, 1H, J = 6.0 Hz), 4.92 – 4.50 (b, 1H), 3.26 (p, 2H, J = 7.2 Hz), 2.13 (m, 2H), 1.16 (t, 3H, J = 7.2 Hz), 1.04 (t, 3H, J = 7.1 Hz) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 192.8, 153.9, 112.6, 108.1, 36.2, 23.6, 15.3, 12.8 ppm
HRMS (ESI)	calcd. for C₈H₁₃NO₂Na [M+Na]⁺, m/z = 178.08385; found, 178.08399

But-3-yn-2-yl hexanoate
Identifier	1E
¹H NMR (600 MHz, CDCl₃)	δ 5.44 (q, 1H, J = 2.0 Hz), 2.43 (d, 1H, J = 2.1 Hz), 2.31 (m, 2H), 1.63 (m, 2H), 1.49 (d, 3H, J = 6.7 Hz), 1.31 (m, 4H), 0.89 (t, 3H, J = 7.4 Hz)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 172.8, 82.4, 72.7, 59.9, 34.4, 31.3, 24.7, 22.4, 21.4, 14.0
HRMS (EI)	calcd. for C₁₀H₁₆O₂ [M]⁺˙ m/z = 168.11448; found, 168.11448

Allene dimer cycloadduct
Identifier	1′2
¹H NMR (600 MHz, CDCl₃)	δ 6.78 (s, 2H), 4.91 (s, 2H), 3.22 (m, 4H), 2.49 (m, 2H), 1.50 (p, 4H, J = 7.5 Hz), 1.36 (s, 4H), 1.18 (d, 6H, J = 6.3 Hz), 0.93 (t, 6H, J = 7.5 Hz) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 153.8, 128.7, 124.3, 41.3, 41.0, 32.1, 29.8, 20.0, 13.8 ppm
HRMS (ESI)	calcd. for C₁₈H₃₁N₂O₄ [M+H]⁺, m/z = 339.22783; found, 339.22725
Empirical formula	C₃₆ H₅₆ N₄ O₈
Formula weight	672.86
Temperature	150 K
Wavelength	1.54180 Å
Crystal system	Triclinic
Space group	P-1
Unit cell dimensions	a = 9.2541(4) Å, α = 82.855(3)°; b = 9.8652(4) Å, β = 82.088(2)°; c = 11.0069(5) Å, γ = 81.487(2)°
Volume	978.76(7) Å³
Z	1
Density (calculated)	1.141 Mg/m³
Absorption coefficient	0.654 mm⁻¹
F(000)	364
Crystal size	0.100 x 0.010 x 0.010 mm³
Theta range for data collection	4.078 to 70.377°
Index ranges	-11<=h<=10, -12<=k<=12, -13<=l<=13
Reflections collected	50711
Independent reflections	3737 [R(int) = 0.092]
Completeness to theta = 70.377°	99.9 %
Absorption correction	Semi-empirical from equivalents
Max. and min. transmission	0.99 and 0.85
Refinement method	Full-matrix least-squares on F2
Data / restraints / parameters	3723 / 78 / 217
Goodness-of-fit on F2	1.0839
Final R indices [I>2sigma(I)]	R1 = 0.0801, wR2 = 0.2443
R indices (all data)	R1 = 0.1087, wR2 = 0.2824
Largest diff. peak and hole	0.55 and -0.47 e.Å⁻³

1-cyclohexylprop-2-yn-1-ol
¹H NMR (400 MHz, CDCl₃)	δ 4.17 – 4.14 (m, 1H), 2.46 (d, 1H, J = 2.4 Hz), 1.87 – 1.76 (m, 5H), 1.70 – 1.66 (m, 1H), 1.61 – 1.52 (m, 1H), 1.31 – 1.02 (m, 5H) ppm
¹³C{¹H} NMR (100 MHz, 400 MHz)	δ 84.1, 73.8, 67.2, 44.0, 28.5, 28.1, 26.5, 26.0, 25.9 ppm

Alkyne small-molecule repeat unit model
Identifier	RU
¹H NMR (400 MHz, CDCl₃)	δ 5.14 (m, 2H, a), 4.79 (t, J = 6.4 Hz, 1H, c), 4.60 – 4.41 (m, 1H, d), 3.93 – 3.56 (m, 1H e, e), 3.36 – 3.15 (m, 0.4H, f), 2.93 (d, J = 6.6 Hz, 1.6H, f), 2.44 (m, 2H, b), 1.91 – 1.59 (b, 15H, g, h, i, j), 1.31 – 0.88 (b, 26H, k, l, m, n, o) ppm
¹³C{¹H} NMR (100 MHz, 400 MHz)	δ 156.1(4), 154.9(5), 80.8(2), 74.2(1), 68.9(3), 55.1(14), 47.1(7), 46.4(8), 44.9(6), 42.0(9, 15), 36.5(12), 35.1(10), 32.0(11), 28.5(16), 28.1(16), 27.7(13), 26.3(17), 25.8(18), 23.3(13*) ppm
HRMS (ESI)	calcd. for C₃₀H₄₆N₂O₄Na [M+Na]⁺, m/z = 521.3355; found, 521.3335

Allene small-molecule repeat unit model
Identifier	RU′
¹H NMR (400 MHz, CDCl₃)	δ 7.35 (m, 2H, b), 5.81 (q, J = 6.0 Hz, 2H, a), 4.95 (b, 1H, c), 4.66 (b, 1H, d), 3.83 (m, 1H, e, e), 3.38 – 2.94 (b, 2H, f, f), 2.16 – 2.00 (b, 2H, g), 1.80 – 1.61 (b, 14H, h, i, j), 1.31 – 0.82 (b, 28H k, l, m, n, o) ppm
¹³C{¹H} NMR (100 MHz, 400 MHz)	δ 192.1(2), 154.5(4), 153.3(5), 112.9(1), 112.2(3), 55.0(14), 47.0(7), 46.2(8), 45.0(6), 41.8(9), 38.7(15), 36.5(12), 35.1(10), 32.4(16), 32.0(11), 27.7(13), 26.2(17), 26.0(18), 23.4(13*) ppm
HRMS (ESI)	calcd. for C₃₀H₄₆N₂O₄Na [M+Na]⁺, m/z = 521.3355; found, 521.3349

Poly(propargylic urethane)
Identifier	P1
¹H NMR (600 MHz, CDCl₃)	δ 5.17 (m, 36.5H, a), 5.04 – 4.76 (b, 18.1H, c), 4.73 – 4.38 (b, 18.9H, d), 4.17 (m, 2.0H, n), 3.88 – 3.62 (b, 19.6H, e), 3.37 – 2.74 (b, 37.7H, f), 2.46 (s, 36.3H, b), 2.00 – 1.81 (b, 80.7H, h), 1.80 – 1.61 (b, 82.2H, g, i), 1.27 – 1.11 (b, 94.0H, j, l), 1.10 – 0.98 (b, 125.2H, h, k), 0.95 – 0.83 (b, 108.6H, m)
¹³C{¹H} NMR (150 MHz, 600 MHz)	δ 156.0 (4), 154.8(5), 80.6(2), 74.5(1), 68.5(3), 66.7(17) 55.1(14), 47.1(7), 46.3(8), 44.9(6), 43.7, 41.9 (9), 41.6(14), 36.5(12), 35.2(10), 32.0(11), 29.8, 27.7(13), 27.6(16), 27.5(16), 27.0, 23.4(13*) ppm
GPC-MALS (THF, 35 °C)	Mn = 6.41 kg/mol, Mw = 26.0 kg/mol, Đ = 4.06, dn/dc = 0.128 mL/g, DP = 15.5
GPC-MALS after hydrolysis	Mn = 6020 g/mol, based upon PS standards
TGA decomposition temperature at 5 % mass loss	266 °C
Isothermal TGA remaining mass (300 °C, 2 h)	73 wt%
Glass transition temperature	162 °C
Melting transition (DSC)	Not observed
Glass transition temperature (25 wt% TXIB)	71 °C
Reduced modulus	1.74 ± 0.04 GPa

Poly(allenylic urethane)
Identifier	P1′
¹H NMR (600 MHz, CDCl₃)	δ 7.36 (m, 16.0H, b), 5.83 (m, 16.9H, a), 5.17 (m, 10.6H, a), 5.05 – 4.50 (b, 25.5H, c, d, c, d), 4.19 (m, 2.0H, n) 3.92 – 3.63 (b, 17.0H, e), 3.44 – 2.79 (b, 31.7H, f), 2.46 (s, 10.9H, b), 2.10 – 1.98 (b, 23.1H, g), 1.97 – 1.83 (b, 64.2, h), 1.79 – 1.61 (b, 48.1H, g, i), 1.24 – 1.11 (b, 83.0H, j, l), 1.11 – 0.98 (b, 109.1H, h, k), 0.97 – 0.86 (b, 98.6H, m)
¹³C{¹H} NMR (150 MHz, CDCl₃)	δ 192.2(2), 154.5(4), 153.2(5), 113.0(1), 111.5(3), 80.6(2), 74.5(1), 74.0, 68.6(3), 66.9(17), 55.1(14), 47.1(7), 46.3(8), 45.1(6), 43.5, 41.8(9), 41.5(15), 38.6, 38.3(15), 36.6(12), 35.2(10), 32.0(11, 16), 29.9, 28.0(16), 27.8(13), 27.5(16), 23.4(13*) ppm
GPC-MALS (THF, 35 °C)	Mn = 7.39 kg/mol, Mw = 11.7 kg/mol, Đ = 1.58, dn/dc = 0.134, DP = 17.9
Alkyne resonances	roughly 35 %
TGA decomposition temperature at 5 % mass loss	232 °C
Isothermal TGA remaining mass (300 °C, 2 h)	75 wt%
DSC first heating cycle	exothermic transition starting at roughly 90 °C
Melting transition (DSC)	Not observed
Glass transition (DSC)	Not observed
Remaining Ag (ICP-MS)	0.549 w/w% Ag; 0.29 mol% Ag relative to olefins
Reduced modulus	4.50 ± 0.15 GPa

Cross-linked poly(allenylic urethane)
Reduced modulus	5.14 ± 0.46 GPa

P1-to-P1′ SOR
Identifiers	P1 and P1′
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C), reaction A	time (h), integration allene (7.36 ppm), integration allene (5.83 ppm), integration alkyne (5.17 ppm), integration alkyne (2.46 ppm), total integration, percent conv. (to allene), conc. of alkyne (M), conc. of allene (M), 1st order eq. y-axis, normalized total integration (× 0.1 M): 0, 0.00, 0.00, 2.54, 2.60, 5.14, 0 %, 0.100, 0.000, 0.00, 0.099; 3, 0.18, 0.18, 2.32, 2.34, 5.02, 7 %, 0.093, 0.007, 0.12, 0.097; 6, 0.34, 0.35, 2.16, 2.33, 5.18, 13 %, 0.087, 0.013, 0.23, 0.097; 9, 0.55, 0.55, 2.03, 2.12, 5.25, 21 %, 0.079, 0.021, 0.39, 0.101; 12, 0.67, 0.66, 1.94, 2.04, 5.31, 25 %, 0.075, 0.025, 0.49, 0.102; 24, 1.05, 1.09, 1.46, 1.56, 5.16, 41 %, 0.059, 0.041, 1.03, 0.099; 36, 1.39, 1.36, 1.30, 1.32, 5.37, 51 %, 0.049, 0.051, 1.57, 0.103; 48, 1.46, 1.51, 1.06, 1.12, 5.15, 58 %, 0.042, 0.058, 2.23, 0.099; 60, 1.49, 1.59, 0.97, 1.04, 5.09, 61 %, 0.039, 0.061, 2.76, 0.098; 72, 1.59, 1.67, 0.96, 1.10, 5.32, 61 %, 0.039, 0.061, 2.97, 0.102
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C), reaction B	time (h), integration allene (7.36 ppm), integration allene (5.83 ppm), integration alkyne (5.17 ppm), integration alkyne (2.46 ppm), total integration, percent conv. (to allene), conc. of alkyne (M), conc. of allene (M), 1st order eq. y-axis, normalized total integration (× 0.1 M): 0, 0.00, 0.00, 2.52, 2.58, 5.10, 0 %, 0.100, 0.000, 0.00, 0.097; 3, 0.17, 0.18, 2.34, 2.33, 5.02, 7 %, 0.093, 0.007, 0.11, 0.096; 6, 0.35, 0.33, 2.14, 2.21, 5.03, 14 %, 0.086, 0.014, 0.24, 0.096; 9, 0.50, 0.50, 2.05, 2.04, 5.09, 20 %, 0.080, 0.020, 0.36, 0.097; 12, 0.67, 0.65, 1.93, 2.06, 5.31, 25 %, 0.075, 0.025, 0.49, 0.101; 24, 1.10, 1.07, 1.51, 1.52, 5.20, 42 %, 0.058, 0.042, 1.04, 0.099; 36, 1.39, 1.45, 1.36, 1.39, 5.59, 51 %, 0.049, 0.051, 1.54, 0.106; 48, 1.43, 1.50, 1.13, 1.23, 5.29, 55 %, 0.045, 0.055, 1.95, 0.101; 60, 1.55, 1.66, 1.06, 1.15, 5.42, 59 %, 0.041, 0.059, 2.47, 0.103; 72, 1.59, 1.67, 1.07, 1.07, 5.40, 60 %, 0.040, 0.060, 2.72, 0.103
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C), reaction C	time (h), integration allene (7.36 ppm), integration allene (5.83 ppm), integration alkyne (5.17 ppm), integration alkyne (2.46 ppm), total integration, percent conv. (to allene), conc. of alkyne (M), conc. of allene (M), 1st order eq. y-axis, normalized total integration (× 0.1 M): 0, 0.00, 0.00, 2.55, 2.56, 5.11, 0 %, 0.100, 0.000, 0.00, 0.098; 3, 0.21, 0.16, 2.32, 2.33, 5.02, 7 %, 0.093, 0.007, 0.12, 0.096; 6, 0.34, 0.32, 2.07, 2.29, 5.02, 13 %, 0.087, 0.013, 0.23, 0.096; 9, 0.56, 0.57, 2.08, 2.15, 5.36, 21 %, 0.079, 0.021, 0.40, 0.103; 12, 0.68, 0.71, 1.94, 2.06, 5.39, 26 %, 0.074, 0.026, 0.51, 0.103; 24, 1.16, 1.16, 1.51, 1.56, 5.39, 43 %, 0.057, 0.043, 1.10, 0.103; 36, 1.41, 1.41, 1.23, 1.21, 5.26, 54 %, 0.046, 0.054, 1.77, 0.101; 48, 1.50, 1.58, 1.06, 1.06, 5.20, 59 %, 0.041, 0.059, 2.49, 0.100; 60, 1.60, 1.67, 1.02, 1.00, 5.29, 62 %, 0.038, 0.062, 3.14, 0.101; 72, 1.59, 1.64, 0.91, 0.91, 5.05, 64 %, 0.036, 0.064, 4.62, 0.096
¹H NMR reaction monitoring averages	time (h), integration allene (7.36 ppm), integration allene (5.83 ppm), integration alkyne (5.17 ppm), integration alkyne (2.46 ppm), total integration, percent conv. (to allene), conc. of alkyne (M), conc. of allene (M), 1st order eq. y-axis, normalized total integration (× 0.1 M): 0, 0.00, 0.00, 2.54, 2.58, 5.12, 0 %, 0.100, 0.000, 0.00, 0.098; 3, 0.19, 0.17, 2.33, 2.33, 5.02, 7 %, 0.093, 0.007, 0.12, 0.096; 6, 0.34, 0.33, 2.12, 2.28, 5.08, 13 %, 0.087, 0.013, 0.23, 0.097; 9, 0.54, 0.54, 2.05, 2.10, 5.23, 21 %, 0.079, 0.021, 0.38, 0.100; 12, 0.67, 0.67, 1.94, 2.05, 5.34, 25 %, 0.075, 0.025, 0.50, 0.102; 24, 1.10, 1.11, 1.49, 1.55, 5.25, 42 %, 0.058, 0.042, 1.05, 0.101; 36, 1.40, 1.41, 1.30, 1.31, 5.41, 52 %, 0.048, 0.052, 1.62, 0.100; 48, 1.46, 1.53, 1.08, 1.14, 5.21, 57 %, 0.043, 0.057, 2.20, 0.101; 60, 1.55, 1.64, 1.02, 1.06, 5.27, 61 %, 0.039, 0.061, 2.76, 0.101; 72, 1.59, 1.66, 0.98, 1.03, 5.26, 62 %, 0.038, 0.062, 3.15, 0.101
Equilibrium concentration used for first-order equilibrium kinetic plot	Equilibrium concentration of alkyne set to 0.354 M (64.6 % conv. to allene) to maximize R2 of line of best fit
GPC-MALS reaction monitoring (dn/dc = 0.130 mL/g)	time, Mn (kg/mol), Mw (kg/mol), Đ: 0 h, 5.57, 26.0, 4.51; 24 h, 9.77, 22.1, 2.26; 48 h, 15.8, 34.0, 2.25; 72 h, 14.9, 136, 9.11

Solid-state SOR of P1
Identifier	P1
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C; 65 °C, 30 min), varying TXIB	wt% TXIB, replicate, integration allene (5.83 ppm), integration alkyne (5.17 ppm), total integration (rel. to TXIB at 4.74 ppm), percent conv. to allene: 0 %, A, 0.03, 1.00, 1.03, 3 %; 0 %, B, 0.04, 1.00, 1.04, 4 %; 0 %, C, 0.05, 1.00, 1.05, 5 %; 10 %, A, 0.60, 9.37, 9.97, 6 %; 10 %, B, 0.58, 9.86, 10.44, 6 %; 10 %, C, 0.54, 10.34, 10.88, 5 %; 15 %, A, 0.77, 7.08, 7.85, 10 %; 15 %, B, 0.67, 6.81, 7.48, 9 %; 15 %, C, 0.80, 6.78, 7.58, 11 %; 25 %, A, 0.73, 3.12, 3.85, 19 %; 25 %, B, 0.55, 2.82, 3.37, 16 %; 25 %, C, 0.61, 2.94, 3.55, 17 %; 50 %, A, 0.28, 0.85, 1.13, 25 %; 50 %, B, 0.25, 0.80, 1.05, 24 %; 50 % C, 0.25, 0.82, 1.07, 23 %
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C; 25 wt% TXIB, 30 min), varying temperature	temperature, replicate, integration allene (5.83 ppm), integration alkyne (5.17 ppm), total integration (rel. to TXIB at 4.74 ppm), percent conv. to allene: 45 °C, A, 0.10, 3.30, 3.40, 3 %; 45 °C, B, 0.13, 3.31, 3.44, 4 %; 45 °C, C, 0.12, 3.16, 3.28, 4 %; 55 °C, A, 0.28, 3.29, 3.57, 8 %; 55 °C, B, 0.22, 3.04, 3.26, 7 %; 55 °C, C, 0.30, 2.79, 3.09, 10 %; 65 °C, A, 0.39, 2.92, 3.31, 12 %; 65 °C, B, 0.39, 2.71, 3.10, 13 %; 65 °C, C, 0.36, 3.28, 3.64, 10 %; 75 °C, A, 0.88, 2.43, 3.31, 27 %; 75 °C, B, 0.77, 2.27, 3.04, 25 %; 75 °C, C, 0.87, 2.53, 3.40, 26 %; 85 °C, A, 0.75, 1.90, 2.65, 28 %; 85 °C, B, 0.99, 2.27, 3.26, 30 %; 85 °C, C, 0.75, 1.60, 2.35, 32 %
¹H NMR reaction monitoring (600 MHz, CDCl₃, 23 °C; 25 wt% TXIB, 65 °C), varying time	time, replicate, integration allene (5.83 ppm), integration alkyne (5.17 ppm), total integration (rel. to TXIB at 4.74 ppm), percent conv. to allene: 5 min, A, 0.24, 2.91, 3.15, 8 %; 5 min, B, 0.26, 3.07, 3.33, 8 %; 5 min, C, 0.26, 3.32, 3.58, 7 %; 10 min, A, 0.41, 2.87, 3.28, 13 %; 10 min, B, 0.34, 2.96, 3.30, 10 %; 10 min, C, 0.32, 2.56, 2.88, 11 %; 30 min, A, 0.91, 3.00, 3.91, 23 %; 30 min, B, 0.80, 2.58, 3.38, 24 %; 30 min, C, 0.75, 2.82, 3.57, 21 %; 60 min, A, 0.95, 2.67, 3.62, 26 %; 60 min, B, 0.91, 2.55, 3.46, 26 %; 60 min, C, 0.91, 2.46, 3.37, 27 %; 120 min, A, 0.97, 2.66, 3.63, 27 %; 120 min, B, 0.86, 2.26, 3.12, 28 %; 120 min, C, 0.85, 2.46, 3.31, 26 %

(1R,4R)-cyclohexane-1,4-dicarbaldehyde
¹H NMR (600 MHz, CDCl₃)	δ 9.65 (s, 2H), 2.23 (m, 2H), 2.11 (m, 4H) 1.36 (m, 4H) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz, CDCl₃)	δ 203.6, 49.4, 24.7 ppm

Protected monomer
¹H NMR (600 MHz, CDCl₃)	δ 4.16 (t, 2H, 5.6 Hz), 1.94 (m, 4H), 1.82 (b, 2H), 1.52 (m, 2H), 1.15 (m, 4H), 0.17 (s, 18H) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz, CDCl₃)	δ 105.7, 90.6, 67.5, 43.9 28.0, 27.9, 27.3, 27.3, 0.06 ppm
HRMS (ESI)	calcd. for C₁₈H₃₂O₂Si₂NH₄ [M+NH₄]⁺, m/z = 354.22791; found, 354.22805

Monomer
Identifier	M1
¹H NMR (600 MHz, CDCl₃)	δ 4.19 (m, 2H), 2.48 (d, 2H, J = 1.3 Hz), 1.97 (m, 4H), 1.78 (b, 2H), 1.57 (m, 2H), 1.18 (m, 4H) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz, CDCl₃)	δ 83.8, 74.0, 66.9, 43.8, 27.7, 27.2 ppm
¹H NMR (600 MHz, CD₃CN)	δ 4.06 (dd, 2H, J = 6.3 Hz, 2.1 Hz), 2.64 (d, 2H, J = 2.1 Hz), 2.22 (b, 2H), 1.90 (m, 4H), 1.43 (m, 2H), 1.08 (m, 4H) ppm
¹³C{¹H} NMR (150 MHz, 600 MHz, CD₃CN)	δ 85.4, 74.1, 66.7, 44.8, 28.5, 28.1 ppm
HRMS (ESI)	calcd. for C₁₂H₁₆O₂Na [M+Na]⁺, m/z = 215.10425; found, 215.10457

Poly(allenylic urethane) hydrolysis products
¹H NMR (600 MHz, CDCl₃)	δ 9.50 (m, 1.00H, a), 6.77 (dd, 1.01H, J = 15.7, 6.6 Hz, c), 6.09 (dd, 0.95H, J= 15.7, 7.9 Hz, b), 5.82 (b, 1.07H), 2.27 (m, 1.47H, d), 1.96 (m, 2.86H, e¢) 1.75 (b, 5.17H), 1.30 (m, 5.67H, e¢) ppm
¹³C{¹H} NMR (150 MHz, CDCl₃)	δ 193.4(1), 161.3(3), 130.1(2), 39.2(4), 29.8(5) ppm

Allene small-molecule repeat unit model hydrolysis products
¹H NMR (400 MHz, CDCl₃)	δ 10.07 (d, 0.20H, J= 8.0 Hz, a), 9.49 (d, 1.80H, J= 8.0 Hz, a), 6.80 (dd, 1.77H, J= 15.9, 6.6 Hz c), 6.46 (t, 0.13H, J= 11.2 Hz c), 6.10 (ddd, 1.68H, J= 15.8, 7.7, 1.3 Hz, b), 5.82 (m, 0.42H, b*), 2.81 (b, 5.37H) , 2.28 (m, 1.97H, d) 1.91 – 1.53 (b, 17.21H) 1.43 – 0.80 (b, 24.11H)
¹³C{¹H} NMR (100 MHz, CDCl₃)	δ 194.7(1), 164.0(3), 158.8, 130.7(2), 85.8, 77.4, 41.0(4), 31.6, 26.0(5), 25.8(6), 25.4(7) ppm