An enzyme-catalysed access to amphiphilic triblock copolymer of PCL-b-PEG-b-PCL: synthesis, characterization and self-assembly properties

Figures & data

Figure 1. SEC traces of PCL-b-PEG-b-PCL and PEG homopolymer.

Table 1. Molecular weight of the as-prepared PCL_N-b-PEG_M-b-PCL_N copolymers determined by SEC and ¹H NMR.

Polymer	Mn (g/mol)^a	Mn (g/mol)^b	PDI (Mn/Mw)^a	Measured N^a	Measured N/M^a	Feeding N/M^b
PCL45-b-PEG45-b-PCL45	11,900	12,200	1.28	43	0.96	1.0
PCL90-b-PEG45-b-PCL90	19,000	22,500	1.39	75	1.67	2.0
PCL90-b-PEG90-b-PCL90	18,000	24,500	1.59	62	0.69	1.0
PCL135-b-PEG135-b-PCL135	19,000	36,800	1.37	57	0.42	1.0

^a Determined by SEC.

^b Theoretical value calculated according to the feeding ratio of [ε-CL]/[PEG] (N/M).

Figure 2. FTIR spectra of PCL, PEG and PCL₄₅-b-PEG₄₅-b-PCL₄₅.

Figure 3. ¹H NMR spectra of PCL-b-PEG-b-PCL, PEG and PCL in CDCl₃.

Figure 4. DSC plots of PCL-b-PEG-b-PCL during (a) cooling of melt and (b) heating.

Table 2. The thermal parameters of PCL-b-PEG-b-PCL determined by DSC.

Polymer	CPCL (wt%)	Tc (°C)	Hc (J/g)	Tm (°C)	Hm (J/g)
PCL43-b-PEG43-b-PCL43	83.2	27.1	−72.51	56.6	73.21
PCL62-b-PEG90-b-PCL62	78.9	25.9	−64.53	58.5	68.63
PCL57-b-PEG135-b-PCL57	66.7	26.3	−76.66	57.9	74.21
PCL	100	24.8	−74.26	59.0	73.09
PEG	0.0	36.1	−175.9	61.4	201.3

Figure 5. XRD diffraction plots of PCL-b-PEG-b-PCL after cold crystallization.

Figure 6. (a) Fluorescence emission spectra of pyrene in water with changed concentration of PCL₄₃-b-PEG₄₅-b-PCL₄₃; (b) plot of Log C versus emission intensity ratio of I₃/I₁.

Table 3. The CMC and D_H of PCL-b-PEG-b-PCL micelles with changing chain lengths of PEG and PCL.

Polymer	CPEG (wt%)	Mn (g/mol)^a	CMC (×10^3, g/L)^b	DH^c	PDI^c	LPEG/LPCL^a
PCL74-b-PEG45-b-PCL74	10.5	19,000	1.12	–	–	0.30
PCL43-b-PEG45-b-PCL43	16.8	11,900	1.42	109	0.082	0.52
PCL35-b-PEG45-b-PCL35	0.20	10,000	1.58	–	–	0.64
PCL57-b-PEG135-b-PCL57	31.6	19,000	1.61	98	0.087	1.18
PCL48-b-PEG90-b-PCL48	26.7	15,000	–	89	0.102	–
PCL62-b-PEG90-b-PCL62	22.2	18,000	1.28	101	0.110	0.73
PCL70-b-PEG90-b-PCL70	0.20	20,000	–	156	0.143	0.64

^a Determined by SEC.

^b Determined by fluorescence technique.

^c Determined by DLS in water.

Figure 7. TEM images of micelles formed by (a) PCL₅₇-b-PEG₁₃₅-b-PCL₅₇ and (b) PCL₆₂-b-PEG₉₀-b-PCL₆₂ in water.

Scheme 1. Route and mechanism of the lipase-catalysed ROP of ε-CL.