A synthesis method and application of PNIPAm-HPC thermosensitive smart hydrogel

Abstract

The present invention relates to a synthesis method and application of a PNIPAm-HPC thermosensitive smart hydrogel, comprising the following steps: 1. Adding N-isopropylacrylamide, hydroxypropylcellulose (HPC) and N,N'-methylenebisacrylamide to deionized water respectively and mixing them evenly to obtain a mixed solution; 2. Adding ammonium persulfate to the mixed solution of step 1 and stirring; 3. Adding N,N,N',N'-tetramethylethylenediamine to the mixed solution of step 2 and stirring to obtain a gel solution; 4. Placing it at 20-30°C for 2-3 hours can obtain a PNIPAm-HPC thermosensitive hydrogel. The present invention provides a simple preparation process of a PNIPAm-HPC dual-network thermosensitive hydrogel and a method for easily manufacturing a PNIPAm-HPC smart window, which opens up a new way for building energy conservation.

Description

Technical Field

[0001] The present invention relates to the field of hydrogel synthesis methods, and in particular to a synthesis method and application of a PNIPAm-HPC temperature-sensitive intelligent hydrogel. Background Art

[0002] PNIPAm thermosensitive hydrogel was synthesized by in situ polymerization in deionized water. Since PNIPAm is a single-network thermosensitive hydrogel, its mechanical strength is poor, and its durability and reusability are low; in addition, the thermal response rate of PNIPAm thermosensitive hydrogel is also slow, ΔT sol and ΔT lum It is not ideal and not conducive to practical application. Summary of the invention

[0003] A method for synthesizing a PNIPAm-HPC thermosensitive smart hydrogel comprises the following steps:

[0004] Step 1, adding N-isopropylacrylamide, hydroxypropylcellulose (HPC) and N,N'-methylenebisacrylamide to deionized water respectively and mixing them uniformly to obtain a mixed solution; the mass ratio of the deionized water, N-isopropylacrylamide, hydroxypropylcellulose and N,N'-methylenebisacrylamide is 20:(1-2):(0.05:1.5):(0.01-0.03);

[0005] Step 2, adding ammonium persulfate to the mixed solution of step 1 and stirring, wherein the mass ratio of ammonium persulfate to deionized water is 20:(0.01-0.03);

[0006] Step 3, adding 4-7 μm N,N,N′,N′-tetramethylethylenediamine to the mixed solution of step 2 and stirring to obtain a gel solution;

[0007] Step 4: Place the mixture at 20-30°C for 2-3 hours to obtain the PNIPAm-HPC thermosensitive hydrogel.

[0008] Furthermore, the mass ratio of the deionized water, N-isopropylacrylamide, hydroxypropyl cellulose and N,N'-methylenebisacrylamide is 20:1.34:0.1:0.02.

[0009] Furthermore, in step 2, the mass ratio of ammonium persulfate to deionized water is 20:0.02.

[0010] The application of PNIPAm-HPC thermosensitive smart hydrogel in thermosensitive smart windows is as follows: a layer of PNIPAm-HPC hydrogel is coated on the upper surface of a glass slide, a layer of glass slide is covered on the upper surface of the PNIPAm-HPC hydrogel to form a sandwich structure, and finally the PNIPAm-HPC hydrogel is sealed with a sealant to obtain a PNIPAm-HPC thermosensitive hydrogel smart window.

[0011] The beneficial effects of the present invention are as follows: the present invention uses a physical crosslinking method to prepare a PNIPAm single network thermosensitive hydrogel into a PNIPAm-HPC double network thermosensitive hydrogel, and the prepared PNIPAm-HPC double network thermosensitive hydrogel is well applied to smart windows, and the loss of building energy is well reduced. Compared with the prior art, the PNIPAm-HPC thermosensitive smart material of the present invention has the following advantages: (1) The PNIPAm single network hydrogel is prepared into a PNIPAm-HPC double network hydrogel by a physical crosslinking method, which not only improves the mechanical strength of the PNIPAm thermosensitive hydrogel, but also improves its thermal response rate; the addition of HPC not only solves the problem of volume change after the phase change of the ordinary PNIPAm thermosensitive hydrogel, but also slightly reduces the LCST of PNIPAm. The prepared PNIPAm-HPC double network thermosensitive hydrogel is well applied to smart windows, and the strong mechanical strength can enhance the reusability of the PNIPAm-HPC thermosensitive smart window, which is more conducive to practical application. In addition, the PNIPAm-HPC smart window can achieve excellent optical performance, high light transmittance, high solar modulation, and has excellent energy-saving performance. (2) Different from the previous methods, the physical cross-linking method of the present invention has the characteristics of simple operation, wide range, high efficiency, and environmental protection. (3) The present invention uses N,N,N',N'-tetramethylethylenediamine as a catalyst to accelerate the reaction rate and quickly promote the cross-linking between monomers, so that the formed hydrogel is more transparent, uniform, and more conducive to practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 (a) is a schematic diagram of the synthesis of PNIPAm-HPC composite hydrogel, (b) is the chemical structure of PNIPAm and HPC, (c) is a schematic diagram of the preparation of the hydrogel glass interlayer, and (d) is the solar modulation mechanism of the PNIPAm-HPC smart window. DETAILED DESCRIPTION

[0013] The following is a description of the principles and features of the present invention. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0014] (1) Synthesis of PNIPAm-HPC thermosensitive hydrogel

[0015] like Figure 1 As shown in a, PNIPAm-HPC hydrogel with thermosensitive properties was successfully prepared using PNIPAm and HPC as raw materials through a simple physical cross-linking method. Figure 1 b shows the chemical structures of PNIPAm and HPC. The main steps are as follows:

[0016] ① Add 1.34 g (0.07 mol) of (N-isopropylacrylamide) (NIPAm), 0.1 g (0.03 mol) of hydroxypropylcellulose (HPC) and 0.02 g (0.0014 mol) of N,N'-methylenebisacrylamide (MBA) into 20 ml of deionized water (DI);

[0017] ②Mix evenly;

[0018] ③ Stir for 30-60 minutes to obtain a uniform and transparent solution;

[0019] ④ Add 0.02g ammonium persulfate (APS);

[0020] ⑤Continue stirring for 30-60 minutes;

[0021] ⑥ Add 6 μm N,N,N′,N′-tetramethylethylenediamine (TEMED);

[0022] ⑦Continue stirring for 3 minutes;

[0023] ⑧ Place at room temperature (20°C) for 2-3 hours to obtain PNIPAm-HPC thermosensitive hydrogel;

[0024] Experimental comparison: PNIPAm and HPC were dissolved in deionized water at a mass ratio of 1:10-1:15.

[0025] Example 1: 1:10, the LCST of the thermosensitive material is 31°C

[0026] Example 2: 1:12, LCST of the thermosensitive material is 30.5°C

[0027] Example 3: 1:15, the LCST of the thermosensitive material is 31.5°C

[0028] (2) Preparation of PNIPAm-HPC temperature-sensitive smart window

[0029] This experiment uses a glass slide as a substrate. First, a certain amount of PNIPAm-HPC hydrogel is added to the front of a glass slide, then covered with a layer of glass slide to form a sandwich structure, and finally sealed with a sealant ( Figure 1c). The high-transmittance slide uses a 7101 sailing board with a size of 47.0mm×20.5mm. Samples with thicknesses of 0.5, 0.75, and 0.10mm were successfully produced to obtain the PNIPAm-HPC thermosensitive hydrogel smart window. In addition, the seal is tight to prevent water evaporation, ensuring safety and durability in actual use. The solar modulation mechanism of the PNIPAm-HPC smart window is as follows Figure 1 As shown in (d), the PNIPAm-HPC hydrogel film can remain completely transparent at room temperature below the LCST, but becomes translucent at temperatures above the LCST, which can effectively block solar radiation.

[0030] (3) Characterization

[0031] The present invention utilizes the synergistic effect of hydrophilic and hydrophobic groups and selects appropriate polymer monomers containing two terminal groups to synthesize a functional polymer with low-temperature thermochromic properties.

[0032] pass 1 H-NMR, 13 The chemical structure of new materials is determined by C-NMR, IR, MS, elemental analysis and other characterization methods; the absorption spectrum of new polymers is characterized by UV; the thermophysical properties of polymer materials are characterized by TGA and DSC to determine their glass transition temperature and LCST; the rheological parameters of polymers at different temperatures are determined by rheometer.

[0033] The internal microstructure of the polymer was measured by SEM, TEM, and AFM to explore the construction of the hydrophilic-hydrophobic network interpenetrating structure. The morphology of the smart polymer film was changed by mixing solvents, additives, etc. to determine the effect of morphology on transmittance.

[0034] Characterization of polymer transmittance and ΔT at different temperatures by UV-VIS-NIR sol ,ΔT lum ,ΔT IR changes, thereby determining the thermal insulation and other functional effects of the smart polymer film.

[0035] The mechanical properties of the polymers were studied. Compared with the polymerization of PNIPAm monomers, the physically cross-linked PNIPAm-HPC smart hydrogels have the characteristics of small volume swelling, easy molding, high tensile strength and toughness. Based on our previous research, we have rich experience in synthesizing physically cross-linked network smart polymer hydrogels, and the mechanical properties will be significantly improved.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing PNIPAm-HPC thermosensitive smart hydrogel, characterized in that: The following steps are involved: Step 1, adding N-isopropyl acrylamide, hydroxypropyl cellulose and N,N'-methylenebisacrylamide to deionized water respectively and mixing them evenly to obtain a mixed solution; the mass ratio of the deionized water, N-isopropyl acrylamide, hydroxypropyl cellulose and N,N'-methylenebisacrylamide is 20:1.34:0.1:0.02; Step 2, adding ammonium persulfate to the mixed solution of step 1 and stirring, wherein the mass ratio of deionized water to ammonium persulfate is 20:(0.01-0.03); Step 3, adding 4-7 μM N,N,N′,N′-tetramethylethylenediamine to the mixed solution of step 2 and stirring to obtain a gel solution; Step 4: Place the mixture at 20-30°C for 2-3 hours to obtain the PNIPAm-HPC thermosensitive hydrogel.

2. The synthesis method of PNIPAm-HPC thermosensitive smart hydrogel according to claim 1, characterized in that: In step 2, the mass ratio of ammonium persulfate to deionized water is 20:0.

02.

3. Application of the PNIPAm-HPC thermosensitive smart hydrogel prepared by any method of claims 1-2 in a thermosensitive smart window, characterized in that: The specific application method is: coat a layer of PNIPAm-HPC hydrogel on the upper surface of a glass slide, cover a layer of glass slide on the upper surface of the PNIPAm-HPC hydrogel to form a sandwich structure, and finally seal the PNIPAm-HPC hydrogel with sealant to obtain a PNIPAm-HPC thermosensitive hydrogel smart window.

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