Synthesis and Characterization of pH and Thermo Dual-Responsive Hydrogels with a Semi-IPN Structure Based on N-Isopropylacrylamide and Itaconamic Acid

Abstract

A series of semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized and investigated in this study. Linear copolymer poly(N-isopropylacrylamide-co-itaconamic acid) p(NIPAM-co-IAM), which is formed by copolymerization of N-isopropylacrylamide (NIPAM) and itaconamic acid (IAM, 4-amino-2-ethylene-4-oxobutanoic acid), was introduced into a solution of NIPAM to form a series of pH and thermo dual-responsive p(NIPAM-co-IAM)/pNIPAM semi-IPN hydrogels by free radical polymerization. The structural, morphological, chemical, and physical properties of the linear copolymer and semi-IPN hydrogels were investigated. The semi-IPN hydrogel showed high thermal stability according to thermal gravimetric analyzer (TGA). Scanning electronic microscopy (SEM) images showed that the pore size was in the range of 119~297 µm and could be controlled by the addition ratio of the linear copolymer in the semi-IPN structure. The addition of linear copolymer increased the fracture strain from 57.5 ± 2.9% to 91.1 ± 4.9% depending on the added amount, while the compressive modulus decreased as the addition increased. Moreover, the pH and thermo dual-responsive properties were investigated using differential scanning calorimetry (DSC) and monitoring the swelling behavior of the hydrogels. In deionized (DI) water, the equilibrium swelling ratio of the hydrogels decreased as the temperature increased from 20 °C to 50 °C, while it varied in various pH buffer solutions. In addition, the swelling and deswelling rates of the hydrogels also significantly increased. The results indicate that the novel pH-thermo dual-responsive semi-IPN hydrogels were synthesized successfully and may be a potential material for biomedical, drug delivery, or absorption application.

Synthesis and characterization of poly(N-isopropylmethacrylamide-co-N-isopropylacrylamide) copolymers

“…FTIR spectra of NIPMAM (a), NIPAM (b), EGDM (c) and p(NIPMAM/NIPAM) sample 40/60/3 (d) Transmittance, % In the range of wavenumbers over 3000 cm -1 in the FTIR spectrum of the NIPAM monomer (Fig. 2b), the characteristic absorption band of strong intensity is at the maximum of 3295 cm -1 , which is assigned to valence vibrations of the secondary amino-group, ν(N-H) [41] and the absorption band at 3073 cm -1 , which is a result of asymmetric vibrations of the vinyl group, νas(=C-H). Absorption bands with the maxima at 2971 cm -1 and 2876 cm -1 in the NIPAM FTIR spectrum are the result of asymmetric and symmetric valence vibrations of the C-H bond in the methyl group, respectively [42].…”

Theoretical and Experimental Contributions on the Use of Smart Composite Materials in the Construction of Civil Buildings with Low Energy Consumption

“…Dividing (19) with (4) and applying the expression limit when V m →∞ is obtained (20). The relation between the area and the volume of a sphere is given by (24). Introducing this expression into (22) results (24).…”

“…The relation between the area and the volume of a sphere is given by (24). Introducing this expression into (22) results (24). Using the relations (4)-(6), the expression (24) can be simplified (25).…”

“…Thus, a method of storing energy in walls, ceilings and floors of a building can be obtained by encapsulating phase-shifting materials to capture direct solar energy and increase human comfort by decreasing the internal temperature variation of the air, keeping the temperature closer to the desired value for a longer period of time [21][22][23][24]. Such an ideal PCM material has to meet a number of criteria: have high value of latent heat due to phase change, good thermal conductivity, high calorific value, and low volume change, and be non-corrosive, non-toxic, and cyclic over time.…”

Rheological Issues of Phase Change Materials Obtained by the Complex Coacervation of Butyl Stearate in Poly Methyl Methacrylate Membranes

“…A possible solution for obtaining a membrane around a phase change material is coacervation, which is a physico-chemical microencapsulation method. The coacervation process is the process of forming macromolecular aggregates following phase separation that happens in a homogeneous polymer solution through the addition of a non-solvent [18][19][20]. Depending on how it is formed, the membrane around the phase transformation material can be used for simple coacervation or complex coacervation.…”