Supporting Information
Elucidation of the Structure of Poly(gbenzyl-Lglutamate)-Nanofibers and Gel-Networks in a Helicogenic Solvent
AnsgarNiehoff1, AlexandreMantion2, RichardMcAloney3, AlexandraHuber2, CynthiaM.Goh3, Jana Falkenhagen2, AndreasF.Thünemann2, MitchellA.Winnik3, HenningMenzel1*
1 Institute for Technical Chemistry, Braunschweig University of Technology, Hans-Sommer-Straße 10, 38106 Braunschweig, Germany, *corresponding author: Prof. Dr. Henning Menzel, Email:
2 BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin, Germany
3Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
Characterization of PBLG
As example for the characterization of the PBLG-samples 1HNMR- (SI-figure 1) and FT-IR-data (SI-figure 2) of PBLG338 are presented. All PBLG samples were characterized by 1HNMR spectroscopy using CDCl3 containing a small amount of trifluoroacetic acid (TFA). The role of TFA is to disrupt the helical conformation adopted by PBLG in chloroform into a coil conformation.1, 2 For PBLG in the coil conformation less broad peaks are obtained. All expected signals were observed (SI-figure 1). The FT-IR spectrum shows all characteristic bands for PBLG: 3290 (NH-valence), 3063/3031 (Aryl-H-valence), 2954 (aliphatic CH-valence), 1734 (C=O, ester), 1652 (C=O-valence, amideI), 1548 (C=O-valence, amideII), 1167 (C-C stretching), 772 (monosubstituted aromat, “out of plane”), 699 (secondary amide, “out of plane” NH-deformation).
SI-figure 1: 1H-NMR of PBLG338 in CDCl3 with the addition of TFA.
SI-figure 2: FT-IR of PBLG338. Sample prepared as solvent-cast film from CHCl3 on a KBr-pellet.
SI-figure 3 shows the SEC-traces of PBLG30 and PBLG338 recorded with light scattering detector and refractive index detector. The traces indicate a monomodal molecular weight distribution with no high or low molecular weight impurities.
SI-figure 3: (A) SEC-trace with 90°-light scattering detector signal of PBLG30 (solid line) and PBLG338 (dashed line). (B) SEC-trace with refractive index detector signal of PBLG30 (solid line) and PBLG338 (dashed line).
SI-figure 4 shows the region for the amideI and amideII bands. The two PBLG-samples PBLG30 and PBLG338 show the same bands at 1653cm-1 and 1548cm-1.
SI-figure 4: FT-IR spectra of PBLG30 and PBLG338. Only the wavenumber region for the amide I and amide II band and the ester band at 1735cm-1 are shown. The samples show the same bands at 1653cm-1 (amideI) and at 1548cm-1 (amideII). The dotted lines show the vibrations, which would be expected for a b-sheet conformation.
Investigation of the morphology of PBLG in toluene at CCgel
SI-figure 5 presents a low magnification TEM-image of dried aggregates of a 0.05 wt% solution of PBLG338 in toluene. The spherical aggregates are fused together and are embedded in a network structure of nanofibers.
SI-figure 5: TEM-image of dried aggregates from a 0.05 wt% solution of PBLG338 in toluene. The spherical aggregates stick together via entanglements of nanofibers.
SI-figure 6 depicts detailed TEM-images of spherical aggregates and their nanofiber corona from a dried sample of a 0.05wt% solution of PBLG338 in toluene.
SI-figure 6: TEM-image of dried aggregates from a 0.05 wt% solution of PBLG338 in toluene. (A) Spherical aggregates merged together and formation of oval aggregates of entangled nanofibers in between aggregates. (B) Two spherical aggregates sticking together and being surrounded by nanofibers like “wool balls”. (C) Two aggregates connected via long nanofibers. (D) Nanofibers radiate from aggregates.
Additional evidence for the ahelical conformation of PBLG in gels by FT-IR
SI-figure 7 shows the FT-IR spectra of dried films of PBLG either solvent cast from CHCl3 or as a dried gel (0.3wt% in toluene). The gel-sample shows the amideI band at 1651cm-1 and the amideII band at 1547cm-1. These values correspond well with the values reported for a-helical structures in literature.3
SI-figure 7: FT-IR spectra of dried films of PBLG338 solvent cast from CHCl3 and a dried PBLG-gel (0.3wt% in toluene). The gel-sample shows the amideI band at 1651cm-1 and the amideII band at 1547cm-1.
Analytical Data for the BLG-NCA used in the synthesis of the PBLG
1H-NMR (CDCl3, 400MHz, d in ppm): 2.11 (m, 1H, H-10a); 2.25 (m, 1H, H-10b); 2.58 (t, 2H, 3J=6.0Hz, H-9); 4.38 (m, 1H, H-11); 5.13 (s, 2H, H-7); 6.75 (s, 1H, NH); 7.36 (m, 5H, phenyl-Hs).
13C-NMR (CDCl3, 100MHz, d in ppm): 26.8 (C-10); 29.7 (C-9); 56.8 (C-11); 67.1 (C-7); 128.3 (C-1 und C-5); 128.5 (C-3); 128.7 (C-2 und C-4); 135.2 (C-6); 152.0 (C-13); 169.4 (C-12); 172.3 (C-8).
FT-IR (KBr, in cm-1): 3257 (CONH-valence), 3089/3065/3042 (Aryl-H-valence), 2935/2859 (CH2, aliphat. CH-valence), 1867/1781 (saturated five membered anhydride ring), 1704 (five membrered lactam ring), 1448 (CH2, CH-deformation), 1256/1187/1113 (COC-valence), 743 (Aryl-H-valence, monosubst. aromatic compound).
EA: N: 5.46 (5.32); C: 59.33 (59.31); H: 5.04 (4.98). (theoretical values in brackets)
SI-table 1: Melting points of the BLG-NCA batches used for the synthesis of PBLG
[Smpman.: manually determined, SmpDSC: determined by DSC (peakmaximum),
n.d.: not determined]
BLG-NCA-5 / 89.5 / n.d.
BLG-NCA-6 / 91 / n.d.
BLG-NCA-7 / 91-91.5 / 94.2
BLG-NCA-8 / 91-92 / 96.1
Literature
1. Quadrifoglio, F.; Urry, D. The Journal of Physical Chemistry 1967, 71, (7), 2364-2366.
2. Crespo, J. S.; Lecommandoux, S.; Borsali, R.; Klok, H. A.; Soldi, V. Macromolecules 2003, 36, (4), 1253-1256.
3. Block, H., Poly(g-Benzyl-L-glutamate) and other Glutamic Acid Containing Polymers, Gordon and Breach, New York. 1983; p 131.
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