Table 2.

Dependence of silk fibroin dissolution in ionic liquid/DMSO binary mixtures on the molecular structure of the IL, the temperature, and the composition of the binary mixture.

Entry	Experimental Variable		Mass % of Dissolved Silk Fibroin, SF-m% a
	Temperature, °C	χ DMSO b	BuMeImAcO c	C3OMeImAcO c	AlBzMe2AcO c	Bu4NAcO c
1	40	0.5	3.0	2.0	0.8	0.3
2	40	0.7	4.0	3.0	1.0	1.0
3	40	0.9	2.0	1.0	0.7	0.5
4	60	0.5	10.0	7.4	0.9	4.0
5	60	0.7	11.0	8.0	3.0	6.0
6	60	0.7	11.5	9.9	3.5	5.0
7	60	0.7	11.5	10.0	3.5	5.0
8	60	0.7	11.5	8.0	3.5	5.9
9	60	0.9	5.5	5.0	2.0	4.8
10	80	0.5	11.0	13.3	7.0	14.0
11	80	0.7	12.0	14.4	8.0	16.0
12	80	0.9	7.0	6.6	4.0	11.0

^a—Mass percent of dissolved silk fibroin = [mass dissolved SF/(mass dissolved SF + mass IL + mass DMSO)] × 100. Based on the results of the central points for which we have more data points, we calculated the uncertainty in SF-m% from [(SF-m%_{maximum value} − SF-_{m%minimum value})/SF-m%_{maximum value}) × 100. Eliminating the (single) worst offender for each IL, we have the following uncertainties: 4.3, 20.0; 14.3, and 16.7% for BuMeImAcO, C₃OMeImAcO, AlBzMe₂NAcO, and Bu₄NAcO, respectively. ^b—χ_DMSO = Concentration of dimethyl sulfoxide in the binary solvent on in the mole fraction scale. ^c—Abbreviations: BuMeIm AcO = 1-(n-butyl)-3-methyimidazolium acetate; C₃OMeIm AcO = 1 1-(2-methoxyethyl)-3-methylimidazolium acetate; Bu₄NAcO = tetra(n-butyl)ammonium acetate; AlBzMe₂AcO = allylbenzyldimethyl ammonium acetate.