A novel route for the synthesis of poly(2‐hydroxyethyl methacrylate) grafted TiO₂ nanoparticles via surface thiol‐lactam initiated radical polymerization

Abstract

Hybrid nanocomposites of poly(2-hydroxyethyl methacrylate) (PHEMA) and TiO 2 nanoparticles were synthesized via surface thiol-lactam initiated radical polymerization by following the grafting from strategy. Initially, TiO 2 nanoparticles were modified by 3-mercaptopropyl trimethoxysilane to prepare thiol functionalized TiO 2 nanoparticles (TiO 2 ASH). Subsequently, surface initiated polymerization of 2-hydroxyethyl methacrylate was conducted by using TiO 2 ASH and butyrolactam as an initiating system. The anchoring of PHEMA onto the surface of TiO 2 nanoparticles was investigated by FTIR, 1 H-NMR, XPS, TGA, and XRD analyses. The experimental results indicated a strong interaction between PHEMA and TiO 2 nanoparticles owing to covalent bonding. The TEM and SEM images of PHEMA-g-TiO 2 showed that the agglomeration propensity of TiO 2 nanoparticles was significantly reduced upon the PHEMA functionalization. The molecular weight and polydispersity index of the cleaved PHEMA from the surface of TiO 2 nanocomposites were estimated by GPC analysis. An improved thermal property of the nanocomposites was observed from TGA analysis. PHEMA-g-TiO 2 nanocomposites were found to be highly dispersible in organic solvents.

Nanocomposites of NR/SBR Blend Prepared by Latex Casting Method: Effects of Nano-TiO2 and Polystyrene-Encapsulated Nano-TiO2 on the Cure Characteristics, Physical Properties, and Morphology

“…By contrast, the additional peaks at 2923, 1726, 1641, 1138, and 1037 cm −1 seen in the spectrum of MPTMS-nTiO 2 (Figure 3(b)) corresponded to the stretching vibration of C-H, C=O, C=C, Si-O, and Ti-OSi bonds, respectively [19][20][21][24][25][26], indicating the binding of methoxy groups in MPTMS to the -OH groups on the nTiO 2 surfaces to introduce double bonds onto the nTiO 2 surfaces, which can further react with the styrene monomer. For the PS-nTiO 2 (Figure 3(c)), the FT-IR spectrum shows the characteristic peaks of PS at 3024 (C-H arom), 2917 and 2850 (-CH 2 -CH 2 ), 1596 (C=C arom), 1492 and 1448 (-C 6 H 5 ), and 908 and 698 (-CH= arm) cm −1 , while the peaks at 1068 and 543 cm −1 were due to the vibration of Ti-O-Si and Ti-OTi bonds, respectively [19,21,23,24,26,27], indicating the existence of PS on the nTiO 2 particle surface. This confirmed the encapsulation of nTiO 2 particles by PS with the aid of MPTMS coupling agent through the free radical copolymerization of styrene monomers with methacrylate groups of MPTMS that chemically bonded with the nTiO 2 core via in situ differential microemulsion polymerization.…”

“…Figure 3 represents the FT-IR spectra of nTiO 2 , MPTMSnTiO 2 , and PS-nTiO 2 in the range of 4000-400 cm −1 . The peak at 3309 cm −1 shown in the spectrum of nTiO 2 (Figure 3(a)) was contributed to the stretching and bending vibration of the -OH groups on the surface of the nTiO 2 particles, which were active sites for the reaction with methoxy groups of the MPTMS [19,21,23,24], while the broad peak at around 665 cm −1 was assigned to the vibration absorption peak of Ti-O and Ti-O-Ti bonds [19,21,23,24]. By contrast, the additional peaks at 2923, 1726, 1641, 1138, and 1037 cm −1 seen in the spectrum of MPTMS-nTiO 2 (Figure 3(b)) corresponded to the stretching vibration of C-H, C=O, C=C, Si-O, and Ti-OSi bonds, respectively [19][20][21][24][25][26], indicating the binding of methoxy groups in MPTMS to the -OH groups on the nTiO 2 surfaces to introduce double bonds onto the nTiO 2 surfaces, which can further react with the styrene monomer.…”

“…The peak at 3309 cm −1 shown in the spectrum of nTiO 2 (Figure 3(a)) was contributed to the stretching and bending vibration of the -OH groups on the surface of the nTiO 2 particles, which were active sites for the reaction with methoxy groups of the MPTMS [19,21,23,24], while the broad peak at around 665 cm −1 was assigned to the vibration absorption peak of Ti-O and Ti-O-Ti bonds [19,21,23,24]. By contrast, the additional peaks at 2923, 1726, 1641, 1138, and 1037 cm −1 seen in the spectrum of MPTMS-nTiO 2 (Figure 3(b)) corresponded to the stretching vibration of C-H, C=O, C=C, Si-O, and Ti-OSi bonds, respectively [19][20][21][24][25][26], indicating the binding of methoxy groups in MPTMS to the -OH groups on the nTiO 2 surfaces to introduce double bonds onto the nTiO 2 surfaces, which can further react with the styrene monomer. For the PS-nTiO 2 (Figure 3(c)), the FT-IR spectrum shows the characteristic peaks of PS at 3024 (C-H arom), 2917 and 2850 (-CH 2 -CH 2 ), 1596 (C=C arom), 1492 and 1448 (-C 6 H 5 ), and 908 and 698 (-CH= arm) cm −1 , while the peaks at 1068 and 543 cm −1 were due to the vibration of Ti-O-Si and Ti-OTi bonds, respectively [19,21,23,24,26,27], indicating the existence of PS on the nTiO 2 particle surface.…”

“…Nevertheless, each type of filler affects the final properties of nanocomposites in a different way according to their structural and geometrical characteristics. Among the nanofiller precursors, nanosized TiO 2 (nTiO 2 ) has been widely used as a nonblack filler in the rubber industry due to its special properties such as self-cleaning, nontoxicity, photovoltaic effect, antibacteria, UV absorber, high-performance properties, and physicochemical stability [12,[17][18][19][20][21], However, nTiO 2 particles possess a very high specific surface area with a large number of hydroxyl groups (-OH) on their surfaces, which can cause a strong filler-filler interaction and a high tendency for self-agglomeration when they disperse in rubber matrix [2,12,17,[20][21][22][23][24][25][26]. The uneven dispersion of nTiO 2 leads to the unimproved mechanical properties and thermal stability of the rubber nanocomposites.…”

“…For this reason, nanofillers surfaces are commonly modified chemically to reduce their agglomeration by increasing the filler-matrix interaction, while simultaneously decreasing the filler-filler interaction [17,[20][21][22][23][24][25]. Nowadays, encapsulating inorganic nanoparticles by polymer molecules, forming a core-shell structure, has attracted much attention in the nanotechnology according to the change in their surface characteristics and the improved compatibility with polymers in the nanocomposites [6,[19][20][21][22][23][24][25][26][27]. Moreover, the hybrid nanoparticles can be designed to enhance the mechanical properties, thermal stability, and performance of the nanocomposites by combining the advantages of different materials.…”