Figure 5.

(a) Synthetic strategy used by Sogah and coworkers [96] to generate silk-mimetic polymers based on chain extension of an oligoalanine-PEG-oligoalanine triblock. Self-assembly of silk-mimetic polymers into β-sheet rich crystalline domains as shown by (b) solid-state FTIR and (c) powder XRD. FTIR spectra were obtained for P2 and P3, which are silk-mimetic ALA-PEG polymers were the ALA degree of polymerizations are approximately 4 and 6, respectively. P2 and P3 film samples were made by drop-casting from a 40% w/v solution dissolved in hexafluoroisopropanol. Resolution-enhanced spectra are shown (dotted lines a and c), as well as second derivative spectrums (solid lines b and d), showing the presence of anti-parallel β-sheets based on bands at 1630 and 1692 cm⁻¹. Powder XRD of P2 (solid line a) and P3 (solid line b) shows d spacings of 5.28, 4.41, and 3.77 Å, which are consistent with anti-parallel β-sheet spacings reported for N. clavipes silk. (b) and (c) are Copyright 2001 American Chemical Society, reproduced with permission from [96].