Self-assembled poly(2-ethyl-2-oxazoline)/malonic acid hollow fibers in aqueous solutions

Abstract

Well-defined poly(2-ethyl-2-oxazoline) (PEOX)/Malonic Acid (MA) fibers having hollow tubular morphology were shown to form in aqueous solutions at 25 o C by complexation induced self-assembly between PEOX and MA. The fibers had diameter of ~1-3 m and a wall thickness of ~40 nm. Different interactions between PEOX and MA were identified for complexation as a function of pH. At pH2, when both ends of MA were protonated, H-bonded complexation was the driving interaction in the fiber formation. IR data showed both PEOX -C=O band and MA -COOH band in dried fibers formed at pH2.The downshift in the -C=O stretching of PEOX by as much as 15 cm -1 confirmed the H-bonded complexation. The interaction enthalpy of PEOX and MA was determined by isothermal titration calorimetry (ITC) as -49.38 kJ/mol which is consistent with H-bonding. Thermogravimetric analysis (TGA) of the fibers showed two distinct decomposition temperatures one between 100-150 o C corresponding to MA and the other one at 350-450 o C corresponding to PEOX which also indicated the presence of both components in the fibers. At pH4, when one end of MA was protonated and the other end was ionized, electrostatic complexation between carboxylate (-COO -) group of MA and the amide group of PEOX was the driving interaction in the fiber formation. At pH7, when both ends of MA were ionized, fiber formation was significantly hindered. The results are important in understanding the role of different interactions in the hollow fiber formation mechanism as a function of pH. pH-responsive hollow fibers have great potential to be used in biomedical applications for drug delivery and release purposes.

Tannic Acid-Stabilized Self-Degrading Temperature-Sensitive Poly(2-n-propyl-2-oxazoline)/Gellan Gum Capsules for Lipase Delivery

“…31,34 Further, the asymmetric stretching of COO − groups of TA at 1531 cm −1 is also reduced to a small shoulder peak in the GG/PnPrOx/TA capsule spectrum implying a strong complexation between TA and PnPrOx. 36 All of the major peaks of GG, TA, and PnPrOx were also observed along with a broad band at 3132 cm −1 in GG/PnPrOx/TA capsule spectrum indicating the successful formation of the GG/PnPrOx core and stable H-bonded PnPrOx/TA shell. 3.2.…”

“…Previous investigations on the hydrophobicity of methyl tert-butyl ether in water revealed that the O–H stretching band arising from isolated water molecules appeared at 3693 cm –1 while the peaks appearing at 3573 and 3507 cm –1 could be assigned to the O–H stretching modes of hydrogen-bonded water molecules . The absorption bands corresponding to CO stretching of P n PrOx were lowered from 1642 to 1632 and 1629 cm –1 for the native polymer P n PrOx, GG/P n PrOx, and GG/P n PrOx/TA capsules, respectively, indicating better interaction with TA. , Further, the asymmetric stretching of COO – groups of TA at 1531 cm –1 is also reduced to a small shoulder peak in the GG/P n PrOx/TA capsule spectrum implying a strong complexation between TA and P n PrOx . All of the major peaks of GG, TA, and P n PrOx were also observed along with a broad band at 3132 cm –1 in GG/P n PrOx/TA capsule spectrum indicating the successful formation of the GG/P n PrOx core and stable H-bonded P n PrOx/TA shell.…”

Preparation of Poly (N-Isopropylacrylamide) -Poly (2-Ethyl-2-Oxazoline) and Their Self-Assembly Properties with Dicarboxylic Acid

“…However, water-soluble polymers can be made with weak physical interactions in dilute solutions. It is known that amide groups can form H-bond with carboxyl groups in aqueous solutions (15). In light of the information that this interaction can be successfully used in layer-by-layer pH-sensitive film formation and the water-soluble polymers can be made with weak physical interactions in dilute solutions (16).…”