Magnetic Ordering in an Organic Polymer Andrzej Rajca, Jirawat Wongsriratanakul, and Suchada Rajca

1. Preparation of polymer 1.
2. Magnetic measurements for polymer 1.
3. Numerical fitting of magnetization data (for Fig. 2A, main text).
4. Experimental results addressing possible magnetic impurities:
(a) magnetic background measurements (Supplemental figs. 1 through 4)
(b) ICP and AA analyses (Supplemental table 1)
(c) summary

1. Preparation of polymer 1. Polyether 2 (0.5 - 1 mg), in a home made 5-mm O.D. quartz tube for magnetic measurements (13), was swollen with perdeuterated tetrahydrofuran (THF-d₈, 40 - 60 L), and then treated with excess of Na/K alloy and 15-crown-5 at 283 K for several days. After the visible excess amount of Na/K was removed, iodine (in small portions) was transferred over the vacuum line into the red/purple reaction mixture at 170 - 167 K, until a homogenious green color of polymer 1 was attained (Fig. 1B, main text).

2. Magnetic measurements. MPMS5S SQUID DC/AC magnetometer was used. Multiple magnet resets (and magnet settings) were employed to attain small residual magnetic fields. For the zero-field measurements, typical residual magnetic field was such that the d.c. moment of the sample was less than 20 % of the in-phase component of a.c. moment at the a.c. drive of 0.1 Oe (i.e., residual H 0.02 Oe). Following the magnetization/susceptibility studies, the samples were kept at room temperature for several weeks, until the paramagnetic susceptibility is <1 % of the original value, and, then, the identical sequence of measurements was repeated for point-by-point background correction.

3. Numerical fitting of magnetization data (for Fig. 2A, main text). Numerical fitting of the magnetization (M) vs. magnetic field (H) at T 3.5 K for highly polydisperse distribution of magnetic moments was based upon the following equation: M = M_sat¹[L(_BS₁H/k_BT )] + M_sat²[B₂(_BS₂H/k_BT)] + M_sat³[B₃(_BS₃H/k_BT)] + M_sat⁴[B₄(_BS₄H/k_BT)], where L(_BS₁H/k_BT x₁) and B_i(_BS_iH/k_BT), i = 2 - 4, correspond to Langevin and Brillouin functions. Total of seven variable parameters, which were related to individual magnetizations at saturation, M_satⁱ, i = 1 - 4 and magnetic moments, _BS_i, i = 1 - 3, were employed. One of the moments, _BS₄, was set to 0.5_B to account for the presence of S = 1/2 impurities and to keep the number of variable parameters to a minimum. The optimized values of variable parameters were used to calculate the total magnetization at saturation, M_sat = M_sat¹ + M_sat² + M_sat³ + M_sat⁴ and the average S = (M_sat¹S₁ + M_sat²S₂ + M_sat³S₃ + M_sat⁴S₄)/M_sat. The test for parameter dependence, 1 - (variance of the parameter, other parameters constant)/(variance of the parameter, other parameters changing), gave values of 0.96 for all seven variable parameters, suggesting that the fits were not overparametrized. Coefficients of determination (R²) were 0.9990.

4. Experimental results addressing possible magnetic impurities
(a) Magnetic background measurements.
Following the magnetization/susceptibility studies, the samples were kept at room temperature for several weeks, until the paramagnetic susceptibility is <1 % of the original value, and, then, the identical sequence of measurements was repeated for point-by-point background correction. Both the negligible d.c. magnetic moment and undetectable a.c. susceptibility for such decomposed samples and the background correction preclude interference from magnetic metal impurities. As an example, the plots of raw magnetic data, corresponding to the data in Figures 2A and 4AB (main text), are shown in Supplemental figs. 1 through 4.

(b) ICP and AA analyses.
ICP analyses (Perkin Elmer Plasma 40/400 Emission Spectrometer) were carried out by Jirawat Wongsriratanakul under supervision of Dr. Michael Carlson of Veterinary Diagnostic Toxicology Laboratory and University of Nebraska, Lincoln. AA analyses (Perkin Elmer 460 with HGA500 graphite furnace) were carried out by John Burch of Soil and Plant Analytical Laboratory at University of Nebraska, Lincoln.

For polyradical samples, following measurement of diamagnetic background, the sample tubes were cut open to allow for solvent evaporation. Subsequently, the quartz sample tube with polyradical residue was cut with diamond knife to the size that fit into the Teflon digestion vessel. The samples were digested with concentrated nitric acid (ACS grade, 5 mL) at 65 (C overnight. The digestion solutions were filtered through filter paper (Whatman 541 coarse) and diluted with distilled water to 25 mL. Using freshly obtained calibration curves, all six samples listed in the Supplemental Table 1 were analysed for Ni, Co, Fe, and Pd.

Following ICP analyses, two digest solutions (no. 2 and no. 6, Supplemental table 1) were examined for Ni, Co, and Fe with AA (Supplemental table 2).

Supplemental Table 1. Summary of ICP data. nd = less than detection limit, d = between detection limit and quantitation level
No.	Sample	Description	Ni	Co	Fe	Pd
1	Blank	digestion vessel	nd	nd	d	nd
2**	Tube	quartz sample tube	nd	nd	d	nd
3	JW-18-32.pwash (1.54 mg) *	Polyether 2 (Table 1, run 3)	nd	nd	d	d
4	JW-17-56/tube (1.54 mg) *	Model polyradical, S = 10 (ref 9)	nd	nd	d	nd
5	JW-18-19/tube (0.73 mg) *	Polymer 1, S = 1300, (Table 1, run 1)	nd	d	nd	nd
6**	JW-18-42/tube (0.89 mg) *	Polymer 1, S = 3000, (Table 1, run 3)	nd	nd	d	nd
7	Calibration	Detection limit, ppb Quantitation level, ppb	5 118	1 26	7 72	4 109
*Mass of polyether used for analysis or preparation of analyzed polyradical sample. **These two digests were analyzed by AA (summary below). nd = less than detection limit, d = between detection limit and quantitation level

Supplemental Table 2. Summary of AA data on digests from ICP runs.
No.	ppb Ni	Ppb Co	ppb Fe
2	0.7	0.9	10.8
6	3.3	1.7	23.4

(c) Summary

The above data preclude any significant interference from magnetic metals on the reported magnetic behavior for polymer 1. The strongest evidence is provided by the essentially diamagnetic behavior of thermally decomposed samples of polymer 1. Any residual paramagnetic moment of such samples is below 1 % of the original value and it was accounted for by point-by-point correction of the d.c. data. In particular, this residual moment is below the detection limit for the a.c. measurements at all settings used to obtain the magnetic data for polymer 1.

The metal analyses by ICP/AA suggest the presence of trace amounts of Fe (and/or Co, Pd) in all samples, including empty digestion vessel and empty quartz sample tube. However, their magnetic contribution is very small, if any. For example, 10 ppb of Fe in a 25 mL digest, corresponds to 2.5 ( 10^-7 g of Fe in the sample. Assuming purely ferromagnetic metal Fe with M_sat = 220 emu/g, the dc moment, m 5 ( 10^-5 emu would be expected, about 1 % of M_sat for polymer 1 obtained from 0.52 mg of polyether 2 (the smallest sample size studied).

Supplemental Figure 1. Polymer 1 (from 0.52 mg of polyether 2). D.c raw data for Figure 2A (main text): m = magnetic moment.

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Supplemental Figure 2. Polymer 1 (from 0.52 mg of polyether 2) after 1+ week at room temperature. d.c. background data for Fig. 2A (main text): m = magnetic moment.

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Supplemental Figure 3. Polymer 1 (from 0.52 mg of polyether 2). a.c. raw data for Fig. 4AB: m' = magnetic moment for in-phase component, m" = magnetic moment for out-of-phase component.

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Supplemental Figure 4. Polymer 1 (from 0.52 mg of polyether 2) after 1+ week at room temperature. a.c. background data for Fig. 4AB: m' = magnetic moment for in-phase component, m" = magnetic moment for out-of-phase component.

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