Protocol for the electrochemical polymerization of polyhydrocarbons from chlorinated methanes and an analysis of its polymerization reaction pathway

Summary

The mass production of polyhydrocarbons (PHCs) is achieved through electrochemical polymerization and its synthetic pathway is investigated using a combination of electrochemical techniques, NMR, and Fourier transform infrared (FTIR) spectroscopy. Here, we present a protocol for the electrochemical polymerization of PHCs from chlorinated methanes and an analysis of its polymerization reaction pathway. We describe steps for large-scale synthesis and characterization of PHCs and studying electrochemical polymerization reactions using cyclic voltammetry and chronoamperometry techniques along with NMR and FTIR spectroscopy using isotope-labeled reactants.

For complete details on the use and execution of this protocol, please refer to Seo et al.,¹ Lee et al.,² and Seo et al.³

Graphical abstract

Highlights

• •Detailed preparation and workup process steps for scaled-up production of PHCs
• •Characteristic study on PHC using various spectroscopic techniques
• •Electrochemical analysis on reaction of monomer and solvent at cathode and anode
• •Real-time FTIR and NMR analyses to understand the polymerization reaction mechanism

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

The mass production of polyhydrocarbons (PHCs) is achieved through electrochemical polymerization and its synthetic pathway is investigated using a combination of electrochemical techniques, NMR, and Fourier transform infrared (FTIR) spectroscopy. Here, we present a protocol for the electrochemical polymerization of PHCs from chlorinated methanes and an analysis of its polymerization reaction pathway. We describe steps for large-scale synthesis and characterization of PHCs, studying electrochemical polymerization reactions using cyclic voltammetry and chronoamperometry techniques along with NMR and FTIR spectroscopy using isotope-labeled reactants.

Before you begin

Pre-treatment on electrochemical container

Timing: ∼15 min washing, 12 h drying

• 1.Clean the electrochemical container by washing it with an Alconox detergent solution and deionized (DI) water.
• 2.Treat it with 1.0 M dilute hydrochloric acid, followed by acetone and deionized (DI) water.
• 3.Dry the container in a hot air oven at 80°C for 12 h.

Pre-treatment on electrodes

Timing: ∼15 min washing, 24 h drying

• 4.Wash the stainless steel 316 sheet (working and counter electrode, 20 × 20 cm²) in acetone, isopropyl alcohol and deionized (DI) water for 5 min each and dry in hot air oven at 80°C for 24 h.

Preparation of Ag/AgNO₃ reference electrode

Timing: ∼20 min washing, 12 h drying

• 5.Clean the electrolyte solution holder glass tube and silver wire with 1.0 M dilute hydrochloric acid, acetone, isopropyl alcohol and deionized (DI) water for 5 min reach and dry in hot air oven at 90°C for 12 h.
• 6.Cover the one edge of the electrolyte solution holder glass tube with replaceable porous junction (Ion permeability porous glass)
• 7.Prepare reference electrode stock solution by adding 0.1 M (0.304 g) of LiPF₆ and 0.01 M (0.034 g) silver nitrate (AgNO₃) in 20 mL of acetonitrile solvent and stir them for about 1 h to get homogenous solution.
• 8.Take 2 mL from stock solution and fill into the electrolyte solution holder tube. After that insert the silver wire and seal the holder tube tightly.

Note: Before starting electrochemical experiment, reference electrode should be freshly prepared and kept it in glove box for 24 h.

Key resources table

REAGENT or RESOURCE	SOURCE	IDENTIFIER
Chemicals, peptides, and recombinant proteins
Lithium hexafluorophosphate (LiPF6, battery grade ≥99.99% trace metal basis)	Sigma-Aldrich	CAS: 21324-40-3
Dichloromethane (CH2Cl2, ≥99.5%)	Daejung Chemicals	CAS: 75-09-2
Carbon tetrachloride (CCl4, ≥99.5%)	Sigma-Aldrich	CAS: 56-23-5
Chloroform (CHCl3, ≥99%, containing amylenes as a stabilizer)	Sigma-Aldrich	CAS: 67-66-3
Acetonitrile (CH3CN, 99.8%, anhydrous)	Sigma-Aldrich	CAS: 75-05-8
Deuterated chloroform (CDCl3, 99.8 atom % D)	Sigma-Aldrich	CAS: 865-49-6
Chloroform-D (CDCl3, 99.8%)	Cambridge Isotope Laboratories	CAS: 67-66-3
Acetonitrile-d3 (CD3CN, 99 atom % D)	Alfa Aesar	CAS: 2206-26-0
Deuterium chloride (DCl, 35 wt % in D2O, ≥99 atom % D)	Sigma-Aldrich	CAS: 7698-05-7
Chloroform-13C (13C-CHCl3, 99%)	Cambridge Isotope Laboratories	CAS: 31717-44-9 (labeled)
Deuterium oxide (D2O, 99.9 atom % D)	Sigma-Aldrich	CAS: 7789-20-0
Hydrochloric acid (HCl, 37%)	Sigma-Aldrich	CAS: 7647-01-0
Ethyl acetate	Sigma-Aldrich	CAS: 141-78-6
Acetone, >99.5%	Daejung Chemicals	CAS: 67-64-1
Isopropyl alcohol, >99.5%	Daejung Chemicals	CAS: 67-63-0
Deionized water (DI)	N/A	N/A
Silica gel 60 (0.040–0.063 mm)	Merck	CAS: 7631-86-9
Other
Electrochemical workstation	Gamry Instruments	Ref. 600+ system
DC power supply	Protek	PL-3003T
Ag/AgNO3 non-aqueous reference electrode	Qrins	RE-7N
Stainless steel sheets (SS316) (working and counter electrode)	KwangEun	N/A
Glove box (argon-filled)	N/A	N/A
Digital peristaltic pump	Hansung	N/A
Stirrer	N/A	N/A
Rotary evaporator	N/A	N/A
NMR spectrometer	Bruker	Ascend 400; AVANCE 800
FTIR spectrometer	Agilent	Cary 600 series
Pellet maker	N/A	N/A-
Gel permeation chromatography (GPC)	Agilent	1200/miniDAWN TREOS system
Differential scanning calorimetry (DSC)	TA Instruments	Q200
X-ray photoelectron spectroscopy	Thermo Fisher Scientific	ESCALAB 250Xi instrument

Step-by-step method details

Preparation of chlorinated monomer-containing solutions for mass production

Timing: ∼2.5 h for each monomer solution

This section describes about the preparation of the three different monomer solutions such as chloroform, dichloromethane and carbon tetrachloride in acetonitrile solvent and Lithium hexafluorophosphate (LiPF₆) electrolyte mixture.

• 1.Fill 600 mL of acetonitrile solvent directly into the glass container and dissolve 23 mM (2.09 g) of LiPF₆ in acetonitrile solvent using a magnetic stirrer for 1 h.
• 2.Add 6.2 M (300 mL) of chloroform into the acetonitrile-LiPF₆ electrolyte solution. Stir the solution mixture for 1 h to form a homogeneous solution.
• 3.Follow the aforementioned steps (1 and 2), but in step 2, instead of chloroform, add 240 mL of dichloromethane (6.2 M) and 360 mL of carbon tetrachloride (6.2 M) into the acetonitrile- LiPF₆ electrolyte solution to prepare dichloromethane and carbon tetrachloride-containing reaction solutions, respectively.

Note: All the solvent and electrolytes are kept inside the glove box before use. Since LiPF₆ has better solubility in acetonitrile than chloroform, dichloromethane and carbon tetrachloride, it is important to dissolve LiPF₆ first in acetonitrile to get a homogenous solution.

Large scale electrochemical polymerization of the chlorinated monomer solution

Timing: 24 h

In this section, we explain the experimental setup and detailed procedures involved for continuous monomer loading and its simultaneous electrochemical polymerization to obtain the product in large amount

Note: All experimental setups placed inside an argon-filled glove box. The quartz electrochemical cell (235 mm × 95 mm × 220 mm (l × w × h)) (Figure 1C) consists of working and counter electrodes (stainless steel sheet, active area = 4 × 20 cm²) (see Figure 1B).

• 4.Fill the prepared monomer solution in a monomer container and transfer it to an electrochemical cell using a peristaltic pump.

Note: The peristaltic pump (Figure 1D) is connected to the electrochemical cell to continuously circulate the solution for uniformity of the electrochemical reaction and to transfer monomer and product at the right time.

• 5.Apply a constant DC voltage of -6 V between the working and counter electrode for 24 h at 28°C.
• 6.Collect the product in an empty glass bottle (collection vessel) using a peristaltic pump.

Note: We can repeat steps 4, 5, and 6 for n cycles of reaction in a given overall run.

Figure 1.

PHCs synthesis setup

(A) Schematic diagram of mass production (Reprinted with permission from J. H. Seo et al., (2022)¹).

(B) Optical image of stainless-steel electrode (SS316).

(C) Home-made large electrochemical cell inside the glove box during electrochemical polymerization.

(D) Peristaltic pump.

(E) DC power supply.

Workup process of polymer

Timing: 48 h

In this section, we explain the various steps involved in the separation of PHC polymer from overall product.

The optical photographs of various steps involved in the workup process are shown in Figures 2A–2D.

• 7.Remove the insoluble material in the product by vacuum filtration.
• 8.Evaporate the residual solvent in the remaining product using a rotary evaporator.

CRITICAL: It is recommended to keep a very small amount of residual solvent with the product. Because the electrolyte salt in the product becomes solid without acetonitrile. Thus, the polymer product becomes sticky and becomes very difficult to dissolve in chloroform for the further process. The temperature of the water bath of the rotary evaporator should be kept at 50°C.

• 9.Mix the remaining dried raw product with 100 mL of chloroform to get a diluted raw product.
• 10.Wash the diluted raw product with 100 mL of 3.7% diluted HCl for 5 times using a separation funnel.

CRITICAL: It is recommended to perform washing inside the Fume hood and wear a face mask and eyewear to avoid hazardous gas leaks and injury. During the first addition of the diluted HCl solution to the product in chloroform, the reaction is vigorous and a large amount of gases evolves out. So, gently add the acid and shake slowly.

Note: The electrolyte salts and metal ions are reacted with acid and move to aqueous region. From 1^st wash to 5^th wash with acid, the aqueous region color changes from green to pale orange indicating the change in the amount of removal of electrolyte salts and metal ions.

• 11.Dry the resulting product in chloroform to get solid powder using a hot air oven at 60°C.
• 12.Purify the resulting product using a silica column chromatography technique with chloroform as the eluent.

Note: 1:1 mixture of ethyl acetate and acetone was used rather than chloroform as a mobile phase.

• 13.Extract the final product (Figure 2E) from the eluent using a rotary evaporator and dry in a vacuum at 50°C.

Figure 2.

Workup Process of PHCs

(A) Product after being removed from insoluble material.

(B) Residual solvent removal using a rotary evaporator.

(C) Product wash with 3.7% diluted HCl (aq.) (1^st time).

(D) Product wash with 3.7% diluted HCl (aq.) (5th time).

(E) Final PHC product.

Characterization of polymer by molecular weight measurement, FTIR and ¹H, ¹³C-NMR, DEPT ¹³C-NMR, and ¹H-¹³C HSQC combined with DEPT NMR study

Timing: ∼60 h

In this section, we explain the steps involved in analyzing the PHC using various techniques to identify its structure, molecular weight and thermal stability.

Nuclear magnetic resonance (NMR) measurement

• 14.Take 0.1 g of product and mix it with 0.7 mL of CDCl₃ and fill it in an NMR tube.
• 15.Measure the 1H (Figure 3A), ¹³C-NMR (Figure 3B), DEPT ¹³C-NMR, and ¹H-¹³C HSQC combined with DEPT spectra. Zgig30 pulse sequences (inverse gated decoupling with 30° pulses, T1 = 10 s, pulse width = 12 s) were conducted at 298.2 K and the scan number was 4096.

Note:¹H-NMR spectra were referenced with residual non-deuterated solvent shifts (CHCl₃ = 7.26 ppm) and ¹³C-NMR spectra were referenced to the solvent chemical shift (CHCl₃ = 77.16 ppm)

Figure 3.

Characterization of PHCs

(A) ¹H NMR spectra (B) ¹³C NMR spectra (C) FTIR spectra and (D) DSC curves of PHCs (Reprinted with permission from J. H. Seo et al., (2022)¹).

Fourier transform infrared spectroscopy (FTIR) analysis

• 16.Add 0.1 mL of product with 0.5 g of KBr.
• 17.Prepare PHC-KBr pellets using a hydraulic press.
• 18.Fill the liquid nitrogen 30 min before the start of recording FTIR spectra.
• 19.Place the bare KBr pellet into the sample holder and measure the background signal.
• 20.Place the PHC-KBr pellet in the holder and record the FTIR spectra in the range 4000–400 cm⁻¹ with 4 cm⁻¹ resolution (Figure 3C).

GPC- multi-angle light scattering (MALS)

• 21.Take 0.1 g of product and mix it with 1 mL of tetrahydrofuran (30°C) and eluted at a rate of 1.0 mL/min to PLgel MIXED-C column, 5 micron, 7.5 × 300 mm (×2), PLgel MIXED-E column, 3 micron, 7.5 × 300 mm (×1). The measured molecular weight of PHCs are given in the Table 1.

Note: GPC system was equipped with UV, refractive index and MALS (three-angle) detectors. The MALS-light source was a 60 mW GaAs linearly polarized laser with a wavelength of 658 nm.

Table 1.

GPC-MALS data of PHCs

Monomer	Dn/dc (mL/g)	MALS
		Mn	Mw
CH2Cl2	0.0781 ± 0.0007	-	-
CHCl3	0.0756 ± 0.0012	7.517×103	8.961×103
CCl4	0.0897 ± 0.0015	1.241×104	1.549×104

Reprinted with permission from J. H. Seo et al., (2022).¹

Differential scanning calorimetry (DSC)

• 22.Load 5 mg of sample in an aluminum pan and place it in a sample holder of the instrument.
• 23.Collect the DSC data using a TA Instrument Q200 from −60°C to 60°C with a ramp rate of 10°C/min (Figure 3D).

Study of the evolution of electrochemical polymerization by cyclic voltammetry -initiation step

Timing: ∼6 h for each monomer solution

In this section, we describe the steps involved in the preparation of monomer solvent for cyclic voltammetry experiment to study the cathodic and anodic reactions

Note: Electrochemical reactions are carried out inside an argon-filled glove box. The electrochemical cell consists of a working and counter electrode (stainless steel sheet, 4 × 4 cm²) and an Ag/AgNO₃ non-aqueous reference electrode.

• 24.Fill 60 mL of acetonitrile solvent directly into the electrochemical cell and dissolve 23 mM (0.209 g) of LiPF₆ in acetonitrile solvent using a magnetic stirrer for 1 h.
• 25.Inject 6.2 M (30 mL) of chloroform into the acetonitrile- LiPF₆ mixture solution. Stir the solution mixture for 1 h to form a homogeneous solution.

Note: Follow the aforementioned steps (24 and 25), but in step 25, instead of chloroform, add 24 mL of dichloromethane (6.2 M) and 36 mL of carbon tetrachloride (6.2 M) into the acetonitrile- LiPF₆ mixture solution to prepare dichloromethane and carbon tetrachloride-containing solutions, respectively.

• 26.Collect the cathodic and anodic polarographs data at the cathode and anode using cyclic voltammetry (CV) by sweeping the potential between 0 and −6 V and 0 and +6 V versus the reference electrode at a scan rate of 100 mV/s at 28°C (Figures 4D–4I).

Note: The monomer solutions are stirred at 200 rpm while measuring CV.

Figure 4.

Cyclic voltammetry study and illustration of electrochemical polymerization

(A) Image of the electrochemical cell with three electrode modes.

(B) Gamry potentiostat.

(C) Schematic illustration of electrochemical polymerization using CHCl₃ and CH₃CN with LiPF₆. M is a metal compound released from SS316 (M = Fe, Ni, and Mo), and H⁺ is a proton. Propagated segments are represented by P. Activated monomers, which have radicals, are represented by am (i, j, and n = integer). (Reprinted with permission from J. H. Seo et al., (2023)³) Cyclic voltammetric curves of (D) CH₂Cl₂, (E) CHCl₃, and (F) CCl₄ with the acetonitrile/LiPF₆ solvent by sweeping the potential from −6.0 V to 0.0 V with a scan rate of 100 mV/s. Cyclic voltammetric curves of (G) CH₂Cl₂, (H) CHCl₃, and (I) CCl₄ with the acetonitrile/LiPF₆ solvent by sweeping the potential from 0.0 V to 6.0 V with a scan rate of 100 mV/s. The voltammograms were recorded by repeating the cycle 5 times.

Study the evolution of electrochemical polymerization through FTIR analysis and ¹H-NMR analysis-propagation step

Timing: 27 h

In this section, we describe the steps involved in the collection of samples at time intervals while performing electrochemical polymerization reaction and identifying the intermediate species using FTIR and 1H NMR methods

Note: Electrochemical reactions are carried out inside an argon-filled glove box. The electrochemical cell consists of working and counter electrodes (stainless steel sheet, 4 × 4 cm²). The 6.2 M CHCl₃ in acetonitrile-LiPF₆ mixture is used as a reaction solution for this study. The constant voltage of −6 V is applied between the working and counter electrodes.

FTIR measurement

• 27.Prepare KBr pellets using a hydraulic press. Subsequently, place the prepared pellets inside the glove box.
• 28.Collect 1 mL of sample from the electrochemical cell at a point close to the cathode at a specific time such as 0, 1, 4, 8, 16 and 24 h, and fill it in the glass vial (Figure 5A).
• 29.Immerse the KBr pellets immediately into the vial containing the extracted solution for 1 min.
• 30.Remove the KBr pellets from the glove box and promptly measure the FTIR spectra (Figure 5B).
• 31.Follow the steps 19 and 20 to measure FTIR data.

CRITICAL: FTIR should be measured within minutes of coming out of the glove box to get the proper signals because the solvent evaporates in a short time then no signals are shown in the FTIR spectrum.

Figure 5.

Time based sample collection while performing polymerization and its FTIR study

(A) Schematic diagram to show the collection point of samples very close to the cathode electrode.

(B) FTIR spectra in the range of 4,000–400 cm⁻¹, obtained by extracting solutions from the cell under electrochemical polymerization using CHCl₃ as a monomer at specific times (0, 1, 4, 8, 16, and 24 h). Inset is high-magnitude regions from 2,950 to 2,900 cm⁻¹ in the yellow box. (Reprinted with permission from J. H. Seo et al., (2023)³).

NMR measurement

• 32.Collect 0.1 mL of sample from the electrochemical cell at a point close to the working electrode at a specific time such as 0, 1, 4, 8, 18 and 24 h during electrochemical polymerization by chronoamperometry (Figure 6B).
• 33.Add the extracted solution with 0.7 mL of CDCl₃ NMR solvents in a glove box.
• 34.Filter the mixture using a syringe filter and fill it in an NMR tube.
• 35.Collect the ¹H-NMR spectra immediately (Figure 6C).

Figure 6.

Time based sample collection while performing polymerization and its ¹H-NMR study

(A) Images of change in colors of reaction solution indicating the polymer formation with respect to time.

(B) Collected samples at various times are stored in different vials.

(C) ¹H-NMR spectra using the extracted solution according to the reaction time (0, 1, 4, 8, 18 and 24 h). (Reprinted with permission from J. H. Seo et al., (2023)³).

Study the evolution of electrochemical polymerization using deuterated monomer and solvent – Termination step

Timing: 27 h

In this section, we explain the detailed steps involved in PHC synthesis with deuterated compounds such as monomer and solvent to identify the proton contribution and termination step by ¹H NMR measurement.

Note: The electrochemical cell consists of working and counter electrodes (stainless steel sheet, 4 × 4 cm²).

• 36.Fill 60 mL of acetonitrile/acetonitrile-d₃ solvent directly into the electrochemical cell and dissolve 23 mM (0.209 g) of LiPF₆ in acetonitrile solvent using a magnetic stirrer for 1 h.
• 37.Inject 30 mL of CHCl₃/CDCl₃ into the acetonitrile-LiPF₆ mixture solution. Stir the solution mixture for 1 h to form a homogeneous solution.
• 38.Apply −6 V between working and counter electrode for 24 h having CH₃CN + CDCl₃, CD₃CN + CHCl₃ and CD₃CN + CDCl₃ reaction solutions, respectively.
• 39.Follow the workup process as mentioned in the above workup process (steps 7 to 13).

Note: The one more product synthesized from CD₃CN + CDCl₃ is treated with D₂O and DCl instead of aqueous HCl to identify proton contribution.

• 40.Measure the ¹H-NMR spectra of all the products (follow steps 32 to 35) (Figure 7A).

Figure 7.

¹H-NMR and ¹³C-NMR study using isotope-labeled reactants

(A) ¹H-NMR spectra of PHCs synthesized by (A) CH₃CN + CHCl₃, (B) CH₃CN + CDCl₃, (C) CD₃CN + CHCl₃, (D) CD₃CN + CDCl₃, and (E) CD₃CN + CDCl₃ purified with DCl in deuterium oxide (D₂O).

(B) ¹³C-NMR spectra of PHCs synthesized with (a) 1.1 atom % (black), nominally, 10 atom % (red), and 99 atom % (blue) ¹³C abundances. (Reprinted with permission from J. H. Seo et al., (2022)¹).

Calculation of carbon participation from CHCl₃ and CH₃CN using ¹³C-labeled chemicals

Timing: 27 h

In this section, we explain the detailed steps involved PHC synthesis using ¹³C labeled to identify the carbon contribution by calculating signal-to-noise ratio from ¹³C NMR data.

• 41.Fill 60 mL of acetonitrile solvent directly into the electrochemical cell and dissolve 23 mM (0.209 g) of LiPF₆ in acetonitrile solvent using a magnetic stirrer for 1 h.
• 42.Inject 30 mL of CHCl₃ (natural abundance 1.1 atom % of ¹³C), 27 mL of CHCl₃ + 3 mL of ¹³C-CHCl₃ (10 atom % of ¹³C) or 30 mL of ¹³C-CHCl₃ (99 atom % of ¹³C) into the acetonitrile-LiPF₆ mixture solution. Stir the solution mixture for 1 h to form a homogeneous solution.
• 43.Apply −6 V between working and counter electrode for 24 h.
• 44.Follow the workup process as mentioned in the above workup process (step 7 to 13).
• 45.Mix each product with 0.7 mL of CDCl₃ and measure the ¹³C-NMR spectra (Figure 7B).

Note: The carbon from the chloroform and/or acetonitrile could be calculated by comparing the signal-to-noise ratio (SNR) of 1.1 atom % ¹³C-PHC with the SNRs of the PHCs having different ¹³C concentrations.

The equation to calculate SNR is,

$$SNR=\frac{{N{\gamma }_{exc}{T}_2\left({\gamma }_{\mathit{det}}{B}_0\right)}^{3/2}\sqrt{ns}}{T}$$

N = number of spins in the system (sample concentration).

γ_exc = gyromagnetic ratio of the excited nucleus.

γ_det = gyromagnetic ratio of the detected nucleus.

ns = number of scans.

B₀ = external magnetic field.

T₂ = transverse relaxation time.

T = sample temperature.

Expected outcomes

This protocol presents the study of various steps involved in the electrochemical polymerization of chlorinated methanes with a continuous production system. Synthesis pathways and products are analyzed by various combined analysis tools such as FTIR, isotope-labeled chemicals supported NMR analysis and CV. This protocol provides the possibility of a mass-production system under an electrochemical polymerization process which is a mild and simple synthesis method. In addition, various combined analysis methods and the use of isotope-labeled reactants make enable a deep understanding of the reaction pathway and structure of the product. This method can be applied to the reaction mechanism study of other chemical syntheses.

Limitations

The yield of the PHC is very low so it requires a large amount of monomer solvents to prepare enough PHC samples to do various spectroscopic analyses. This was the main motivation that we built a continuous production system.

Troubleshooting

Problem 1

Moisture, oxygen, and impurities in the chemical solvents and electrolyte salt.

Potential solution

Keep the solvent bottle and electrolyte salt inside the glove box before opening the seal.

Problem 2

The change in standard potential of reference electrode due to contamination of electrolyte from the monomer solvents during the electrochemical study.

Potential solution

Prepare a stock solution of reference electrolyte in advance. Before starting the experiment, every time clean the Ag electrode and change the electrolyte inside of the reference electrode compartment.

Problem 3

Challenges in CV combined in situ FTIR and NMR study such as changing sample condition, NMR signal broadening and EC-NMR circuit interference.

Potential solution

Measure the FTIR and ¹H-NMR within a short time after extracting the sample at various reaction times.

Problem 4

Challenges in the purification of the synthesized polymer through the use of a silica column. Polymer stuck at the top of the silica column.

Potential solution

For the removal of products containing relatively large amounts of nitrogen and chlorine atoms, chloroform was used as a column solvent. For products containing smaller amounts of nitrogen or chlorine, a 1:1 mixture of ethyl acetate and acetone was used (rather than chloroform) as the mobile phase.

Problem 5

There is some undissolved polymer product in the solvent after drying the “purified solution washed with diluted hydrochloric acid 3.7% (100 mL × 5 times) using a separation funnel”.

Potential solution

Do not dry the purified solution completely. Always retain some portion of solvent in which the polymer can be dissolved. Completely dry the product after purification using a silica column.

Resource availability

Lead contact

Further information and requests for resources and reagents should be directed to and will be fulfilled by the lead contact, Sun Hwa Lee (sunhlee@ibs.re.kr; sunhwa.lee82@gmail.com).

Materials availability

Any requests related to data will be fulfilled by the lead contact upon reasonable request.

Data and code availability

This study did not generate any datasets.