Structural and Thermal Analysis of Copper-Doped Poly(N-isopropylacrylamide) Films

Abstract

In the present study, the chemical structure of thermoresponsive copper-doped poly(N-isopropylacrylamide) thin films was investigated. The polymer thin films were deposited by spin-coating from a solution containing the polymer on silicon windows. Spin-coating was carried out at certain conditions yielding films of nanometric-scale thickness (170-250 mn). Thermal transitions such as low critical solution temperature (LCST) and glass transition temperature (T g ) of polymer samples with respect to copper concentrations were studied by the differential scanning calorimetry (DSC) technique. Thermograms show that thermal transitions shift to higher temperatures after doping polymer with Cu þ2 . Heat capacity (Cp, J/g. C) also increases as the concentration of Cu þ2 increases. Fourier transform-infrared (FT-IR) spectrum of pure poly(N-isopropylacrylamide) film exhibits several characteristic stretching bands attributed to V as (NH), amide I (C¼O), and amide II (C-N) respectively. The infrared spectrum of the corresponding Cu þ2 -doped polymer thin films showed a significant shift in the characteristic bands compared to that of pure polymer, indicating a strong interaction between Cu þ2 and poly(N-isopropylacrylamide). The UV-visible spectrum of Cu þ2 -doped poly(N-isopropylacrylamide) shows the creation of a new band positions at 276 nm and 278 nm. These bands are absent in the pure polymer spectrum, indicating a complex formation between Cu þ2 and poly(N-isopropylacrylamide). Coil to swollen aggregate formation was investigated by using the tapping mode atomic force microscopy (AFM) technique. Addition of copper ions to the polymer shows a clear change in the morphology of the polymer thin films compared to the morphology of pure poly(N-isopropylacrylamide) prepared with water as solvent, resulting in clusters that approach single nanoparticle behavior.

Weakly Ionically Bound Thermosensitive Hyperbranched Polymers

“…The differential scanning calorimetry (DSC) curves of S8P8 and S16P16 show glass transition temperatures ( T g ) of 81 and 89 °C, respectively, indicating an amorphous state without signs of crystallization (DSC methodology and curves in Figure S5). The T g values for these compounds are significantly lower than those of regular high-molecular-weight PNIPAM materials (within 110–140 °C). − This depression is due to the low T g of the hyperbranched polyester core with T g values of similar branched polyester polyols reported to be within 25–40 °C. − The hyperbranched polyesters with terminal alkyl fragments obtained in our previous study have a T g value of −30 °C and melting points of 40–60 °C, attributed to the crystalline phase formed by the alkyl component . The absence of melting peaks for S8P8 and S16P16 can be related to the suppression of crystallization of the alkyl branched components by adjacent PNIPAM macrocations …”

Palladium nanoparticles capped by thermoresponsive N‐heterocyclic carbene: Two different approaches for a comparative study

“…The characteristic π → π* transition of PNIPAM moiety appeared at around λ max of 263 nm for the NHC precursor (Figure 3, red curve). [ 52 ] On the other hand, for the NHC–Pd 2+ complex addition to the PNIPAM characteristics band (at around 263 nm), a broad hump appeared at 340 nm due to the presence of d–d transition (metal to ligand charge transfer—MLCT) of Pd (II) (Figure 3, pink curve). [ 53 ] In the case of NHC‐capped Pd NPs (catalysts 2 and 4), appearance of broad continuous bands at lower wavelength confirmed the presence of Pd (0) Nps (Figure 3, black curve).…”

Synthesis and Catalytic Studies of Thermoresponsive Copper (I) Complex towards Click Reactions

“…As a result, we fail to observe a predominant shift in the pyridine peaks as observed in the Pyridyl ‐ Triazole ‐ INT ‐ Cu ( I ) complex . Furthermore, it was seen that the NH, C=O (Amide I), and NH (Amide II) did not show any significant shift, such as shifting in the peak position or intensity variations of Amide I peak upon chelation with the metal, it proved that polymer chains were not involved in the binding with the copper (I) [52] …”

“…Furthermore, it was seen that the NH, C=O (Amide I), and NH (Amide II) did not show any significant shift, such as shifting in the peak position or intensity variations of Amide I peak upon chelation with the metal, it proved that polymer chains were not involved in the binding with the copper (I). [52] Even though FTIR results failed to show significant results, the comparison of 1 H NMR results between thermoresponsive ligand (compound 2) and its copper (I) complex (compound 4) showed changes in the spectrum. Thus, even though the peaks concerning the polymer chain were not shown any shift in the chemical shift values; however, the peaks correspond to the pyridyl and triazole, which comes in the aromatic region, showed a slight shift towards higher chemical shift values, indicating the possibility of the binding of the ligand with the metal (Figure 5).…”