Q200 differential scanning calorimeter

The Fourier transform infrared (FT-IR) spectra were tested by a Bruker VERTEX 80 V FT-IR spectrometer. ¹H NMR spectra were carried out on a 500 MHz Bruker AVANCE III spectrometer. Rheological measurements were performed at 25 °C on a TA Instrument HR-2 rheometer with 40 mm parallel stainless-steel plates. The frequency sweeps were conducted at a constant shear strain of 2% by varying angular frequency from 0.1 to 100 rad/s. The lap-shear strengths were measured by 410R250 Tension Instrument (TestResources Inc., USA) at a stretching speed of 50 mm/min. The digital images were captured by a Canon PowerShot SX40 HS camera. The thermal gravimetric analysis (TGA) measurements were tested on a Q500 thermogravimetric analyzer (TA Instruments) under a nitrogen atmosphere at a heating rate of 10 °C/min. Scanning electron microscopy (SEM) was conducted under vacuum using a Hitachi SU8020 SEM (Tokyo, Japan). Differential scanning calorimetry (DSC) measurements were performed on a TA Instruments Q200 differential scanning calorimeter under a nitrogen flow of 50 mL/min.

DSC analysis was conducted on a Q200 differential scanning calorimeter (TA Instruments, New Castle, Delaware, U.S.A.) using our previously reported procedures [20 (link)]. Briefly, the microemulsion samples were carefully weighed into standard 40 μL aluminum pans and sealed immediately. Pans were quickly cooled from ambient temperature to -90°C; after equilibrating at -90°C for 20 min, the samples were heated from -90°C to 40°C at a rate of 5°C/min. An empty aluminum pan was used as a reference. The thermal behaviors reflecting different water states were analyzed, and the contents of different states of water were calculated by the method established by Senatra et al. [21 ].

Differential scanning calorimetry (DSC) was used to analyze the state of water within the IPNs. To this purpose, dry PCB/PSB IPN was let to swell in distilled water at 25 °C for 72 h. Then, a piece from the swollen IPN sample (~6 mg) was sealed in a DSC T zero aluminum pan and analyzed against an empty pan (control) via Q200 Differential Scanning Calorimeter (TA instruments, USA). Both pans were first cooled to −90 °C and then heated to 160 °C at a heating rate of 10 °C/min. A constant flow of 50 mL/min N₂ gas was purged through the system during the DSC analysis. The amounts of freezable (W_fs) and non-freezable (W_nfs) water were calculated using the following equations [31 ]:


where SR is the swelling ratio of IPN hydrogel, m_s is the weight of the IPN hydrogel after 72 h swelling into the salt solution with respective concentration m_d is weight of the dry network; ΔH°_H2O = 333.5 J/g is the water melting enthalpy and; ΔH_hydrogel is the sum of the melting enthalpies for all endothermic peaks which appear in the DSC heating run; W_fs is the freezable/unbonded water and W_nfs is the non-freezable/bonded water.

¹H NMR spectra were recorded on a JEOL ECS-400 spectrometer (JEOL, Tokyo, Japan) operated at 400 MHz. The number-average molecular weights (M_n) and molecular weight distributions (M_w/M_n) of the product polymers were determined via size-exclusion chromatography (SEC) in DMF containing 100 mM LiCl at 40 °C on two hydrophilic polymer gel columns [Tosoh α-M + α-3000 (7.8 mm i.d. × 30 cm) (Tosoh Corporation, Tokyo, Japan); flow rate of 1.0 mL/min] (for poly(4VG)) connected to a JASCO PU-2080 precision pump and a JASCO RI-2031 detector (JASCO, Tokyo, Japan). The columns were calibrated against standard polystyrene samples (Agilent Technologies, Santa Clara, CA, USA; M_p = 580–3,053,000, M_w/M_n = 1.02–1.23). The glass transition temperature (T_g) of the polymers was recorded on a Q200 differential-scanning calorimeter (TA Instruments, Inc., New Castle, DE, USA), and the T_g values were obtained from the second scan after removing the thermal history. The samples were first heated to 210 °C at 10 °C/min, equilibrated at this temperature for 10 min, and cooled to −60 °C at 5 °C/min. After holding at this temperature for 5 min, the samples were then reheated to 210 or 260 °C at 10 °C/min. The thermogravimetric analyses (TGA) were performed on a Q500 system (TA Instruments Inc.) at 5 °C/min under a N₂ gas flow.