Molecular Weight Distribution of Living Chains in Polystyrene Pre-pared by Atom Transfer Radical Polymerization Joongsuk Oh, a Jiae Kuk, a Taeheon Lee, b Jihwa Ye, b Huyn-jong Paik, b* Hyo Won Lee, c* Taihyun Chang a* a Department of Chemistry and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea b Department of Polymer Science and Engineering, Pusan National University, Busan, 46241, Korea c Department of Chemistry, Chungbuk National University, Cheongju, 28644, Korea Table of Contents Experimental Figure S1: MALDI mass spectra of two different living chains. Figure S2: MALDI mass spectra of living and dead chains. Figure S3: Expanded view of NMR spectra of as-prepared PS-OH and the living chains. Figure S4: HPLC separation of PS-triazole. Figure S5: 3D structure of model molecules for PS-OH.
Experimental Synthesis of PS-Br Styrene (Aldrich, 99%) was passed through the alumina column to remove the inhibitor and stabilizer. Copper(I) bromide (CuBr, Aldrich, 98%) was stirred with glacial acetic acid then filtered and washed with ethanol and diethyl ether in that order. N,N,N,N,N - Pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%, 384 mg), Ethyl α- bromoisobutyrate (EBib, Aldrich 98%, 0.3 mg), and CuBr (290 mg) were added to the flask. The flask was sealed with a rubber septum. Styrene (11 g) and anisole (3 ml) were also added to the flask via syringes. The mixture was degassed three times by vacuum and refilled N 2 gas. The temperature of the flask was kept by oil bath at 100 C for 30 mins. The polymerization was quenched by lowering the temperature and exposing to the air. The reaction mixture was diluted with THF and passed through a neutral alumina column to remove the copper catalysts. The polymer was precipitated in methanol and filtered, then dried under vacuum. Conversion of chain end Sodium azide (NaN 3, Aldrich, 99.5%) was added to a solution of PS-Br in DMF. The mixture was stirred at room temperature for 24 h. The mixture was filtered to remove NaN 3, and the filtered solution was evaporated to remove DMF. The polymer, PS-N 3 was reprecipitated in methanol. Propargyl alcohol (Aldrich, 99%), PS-N 3, CuBr and DMF were added to the flask, and degassed. The temperature of the flask was kept at 25 C. PMDETA, and DMF mixture were also degassed and added to the flask by syringe. After the reaction for 24 hours, the reaction mixture was diluted with THF and filtered to remove the copper catalyst and the polymer, PS- OH was reprecipitated in methanol Size exclusion chromatography (SEC) analysis Three PS/DVB columns (Agilent Polypore 300 7.5 mm, Waters Styragel HR4 300 7.8 mm, and Jordi mixed bed 300 8.0 mm) were used. A Viscotek TDA302 detector was used for differential refractometry (RI) and light scattering (LS) detection. Eluent was THF delivered by a Bischoff HPLC compact pump at a flow rate of 0.7 ml/min. The absolute molecular weight was determined by SEC-LS with the OmniSEC v 5.00 TM program with dn/dc of PS in THF of 0.185. (M w = 3,300, M n = 3,170, Đ = 1.04).
HPLC analysis A bare silica column (Nucleosil, 5 μm, 50 Å, 250 4.6 mm) was used. Mobile phase was a THF/n-hexane mixture (42/58, v/v) delivered by an HPLC pump (Shimadzu LC-20AD) at a flow of 0.5 ml/min. The column temperature was kept at 40 C using a homemade column jacket and a water bath circulator (JulaboF25). Chromatograms were recorded with a UV/Vis absorption detector (YounlinUV730D). All samples for HPLC analysis were dissolved in the eluent at a concentration of 1 mg/ml and the injection volume was 100 µl. For solvent gradient, the eluent was kept for the first 10 min then changed linearly to pure THF during the next 29 min. MALDI- MS analysis A Bruker Autoflex speed mass spectrometer equipped with a 2k Hz smartbeam-ii laser was used for MALDI MS experiments. The instrument operated at an accelerating potential of 20 kv in positive mode. Mass calibration was performed using homemade PS standards. DCTB (trans-2-(3-(4-tert-butylphenyl)-2-methyl-2-propenylidene)malononitrile) were used as MALDI matrix. Either sodium trifluoroacetate or silver trifluoroacetate was used as a cationization agent. Typical sample preparation was performed by making stock solutions in THF of matrix (30 mg/ml), polymer analyte (5 mg/ml), and cationization agent (2 mg/ml). The stock solutions were mixed in a 10/1/1 ratio (matrix/analyte/cation), and deposited onto a MALDI target plate. NMR analysis 1 H NMR spectra were obtained on a Bruker-Spectrospin 300 MHz FT-NMR spectrometer using CDCl 3 as a solvent. Molecular geometry optimization Molecular geometry optimization was performed using DFT calculation (RB3LYP, 6-31G(D)).
Figure S1. MALDI mass spectra of two different living chains (F2 and F3). DCTB matrix and sodium cation were used. PS-OH living chain (calculated m/z of 30mer, C 249 H 255 O 3 N 3 Na + : 3360.0, observed: 3360.0).
Figure S2. MALDI mass spectra of living and dead chains of the ATRP grown PS. DCTB matrix and silver cation were used. PS-OH living chains (calculated m/z of 30mer C 249 H 255 O 3 N 3 Ag + :3444.9, observed: 3444.8), dead chains by coupling (calculated m/z of 30mer C 252 H 265 O 4 Ag + : 3465.0, observed: 3464.0), and dead chains by disproportionation (calculated m/z of 31mer C 254 H 258 O 2 Ag + : 3450.9, C 254 H 260 O 2 Ag + : 3452.9, observed: 3450.9).
Figure S3. Expanded view of NMR peaks of H b and H c of the living PS-OH chains (F2 and F3).The summation of the NMR peaks (green) of F2 and F3 matches well with the NMR peaks of as-prepared PS-OH (black).
Figure S4. HPLC separation of PS-triazole. The same HPLC separation condition as in Figure 2 was used. PS-triazole was prepared by CuAAC click reaction with PS-N 3 and propyne.
Figure S5. 3D structures of the chain end of PS-OH isomers. In case of the (1S, 3S) isomer, two H c protons are close to an internal benzene ring and are in different shielding environments. On the other hands, H c protons in the (1R, 3S) isomer are far from the internal benzene ring.