Hydrolysis of hydrophobic poly(2-oxazoline)s and their subsequent modification via aza-Michael addition

Figures & data

Scheme 1. Overall reaction scheme showing the partial hydrolysis of poly(2-oxazoline)s followed by the subsequent aza-Michael addition.

Table 1. Summary table for the conditions studied for the aza-Michael additions carried out for PEtOx (PE1-PE7) and PFAOx (PF1-PF4.).

Run	Monomer	Equivalents of Base	Equiv. of Monomer	T (°C)	Time (hours)	Functionalisation (%)
PE1	A	1.5	1.5	60	15	20^a
PE2	A	1.5	1.5	120	2	27^a
PE3	A	PE2 (+1.5)	PE2 (+1.5)	120	PE2(+2)	41^a
PE4	A	1.5	1.5	120	15	59^a
PE5	A	5	5	140	5	59^a
PE6	B	1.5	1.5	120	2	21^b
PE7	C	1.5	1.5	120	2	4^b
PF1	A	3	1.5	120	2	56^a
PF2	A	3	1.5	130	2	58^a
PF3	A	3	1.5	120	16	60^a
PF4	A	5	3	130	2	58^a

^aFunctionalisation calculated according to the ratio of -CH₂- of the propargyl group to the hydrolysis peak (equation 3(3) $\mathrm{\%}Functionalisation=\frac{2I_{C{H}_2}}{I_H+2I_{C{H}_2}}$(3) ), ^bFunctionalisation calculated by measuring the reduction in the hydrolysis peak. All reactions were carried out in THF with TEA as base.

Figure 1. a) hydrolysis kinetics showing PFAOx hydrolysed in 8:2 THF/HCl_aq (black), PEtOx hydrolysed in 8:2 THF/HCl_aq (red), PEtOx hydrolysed in 6.3:1.3:2.4 1,4-butanediol/water/HCl_aq (blue), PEtOx hydrolysed in 8:2 THF/HCl_aq at 100 °C (green) and PEtOx hydrolysed in 8:2 water/HCl_aq (purple). b) corresponding first-order kinetic plot. All reactions were carried out with 35–37% HCl_aq such that [H⁺]=2.4 M and [A]=0.48 M. PFAOx hydrolysis was calculated according to Equation 1(1) $DegreeofHydrolysis\left(\mathrm{\%}\right)=100\left(\frac{I_{H,tf}-I_{H,t0}}{I_P}\right)$(1) and all PEtOx hydrolysis rates were calculated according to Equation 12.

Figure 2. a) GPC chromatograms for the hydrolysis of PFAOx, showing the shift to lower molecular weight and the increase in tailing at higher degrees of hydrolysis. b) plot of M_p,GPC with degree of hydrolysis.

Scheme 2. Partial reaction scheme for the thiol-yne click reaction of PE4.

Figure 3. 1H NMR spectrum of PE4 before and after thiol-yne click reaction (a), and the GPC traces (RI detector) of PE4 before and after reaction with thiophenol (b).

Data availability statement

FURTHER DATA WILL BE AVAILABLE UPON REQUEST.