1H nuclear magnetic
resonance (NMR) spectra were conducted on a Bruker Advance 400 MHz
spectrometer in either deuterated chloroform (CDCl3) or
deuterated water (D2O). Gel permeation chromatography (GPC)
was recorded by using a Shimadzu Prominence-I GPC system. The system
was configured with a pLgel-mixed D column and a Shimadzu RID-20A
differential refractive index detector. The used eluent was tetrahydrofuran
(THF) with a flow rate of 1 mL/min, and polystyrene calibration standards
were used. Potentiometric titration of the polymers was performed
in a 20 mL vial with a Mettler Toledo pH meter and a general-purpose
probe. Solutions of polymer (1 mg/mL) were prepared with deionized
water (at room temperature), and 1 M NaOH was added to raise the starting
pH to approximately 12. Titrant HCl (0.01 M) was gradually added with
micropipettes under gentle stirring; after reaching a stable pH value,
the base was again added. The titration curve and the first derivative
of the curve were used to determine the equivalence points and the
pKa, taken at half the equivalence points.
For p(IPMAm), 50/50 ethanol/water was used as solvent
due to polymer precipitation above its pKa in pure water.22 (link),23 (link)
resonance (NMR) spectra were conducted on a Bruker Advance 400 MHz
spectrometer in either deuterated chloroform (CDCl3) or
deuterated water (D2O). Gel permeation chromatography (GPC)
was recorded by using a Shimadzu Prominence-I GPC system. The system
was configured with a pLgel-mixed D column and a Shimadzu RID-20A
differential refractive index detector. The used eluent was tetrahydrofuran
(THF) with a flow rate of 1 mL/min, and polystyrene calibration standards
were used. Potentiometric titration of the polymers was performed
in a 20 mL vial with a Mettler Toledo pH meter and a general-purpose
probe. Solutions of polymer (1 mg/mL) were prepared with deionized
water (at room temperature), and 1 M NaOH was added to raise the starting
pH to approximately 12. Titrant HCl (0.01 M) was gradually added with
micropipettes under gentle stirring; after reaching a stable pH value,
the base was again added. The titration curve and the first derivative
of the curve were used to determine the equivalence points and the
pKa, taken at half the equivalence points.
For p(IPMAm), 50/50 ethanol/water was used as solvent
due to polymer precipitation above its pKa in pure water.22 (link),23 (link)