CN105115952B - A kind of method that fluorescence probe method measures polymer solubility parameters - Google Patents

Abstract

The invention belongs to the field of polymer physics research, and particularly relates to a method for measuring polymer solubility parameters: by synthesizing fluorescent probe molecules and introducing the fluorescent probe molecules into polymer chains, the polymer has a fluorescent effect, and the Detecting the fluorescence behavior of probe molecules can macroscopicize the microcosmic coiled state of polymer chains in solution, and measure the fluorescence spectra of polymers dissolved in solvents with different solubility parameters, thereby determining the polymerization solubility parameters.

Description

A method for measuring polymer solubility parameters by fluorescent probe method

technical field

The invention belongs to the field of polymer physics research, in particular to a method for measuring polymer solubility parameters.

Background technique

The homogeneous mixture formed by polymer dispersed in a solvent in a molecular state is called "polymer solution". The viscosity and stability of the polymer solution have a great influence on the actual application. Therefore, if the polymer is to become a polymer solution, the first problem to be solved is the selection of the polymer solvent.

Three principles for judging the solubility of polymers by solvents: (1) "similar polarity"principle; (2) "similar cohesive energy density (CED) solubility parameters"principle; (3) "polymer-solvent interaction The action parameter χ ₁ is less than 1/2" principle.

The solubility parameter is the square root of the cohesive energy density (δ=(ΔE/V) ^1/2 , ΔE/V is the vaporization energy of a unit volume of liquid into gas at zero pressure), which reflects the intermolecular force of substances A measure of size can also be used to judge the strength of the interaction between different molecules. It essentially reflects the compatibility between substances, and is also a characteristic parameter related to the properties and processing properties of polymers. When the solubility parameters of two substances are closer, the two substances are more compatible.

When selecting a solvent for a polymer, in addition to a single solvent, a mixed solvent can also be used. The solubility parameter _δ of the mixed solvent can be roughly adjusted by Equation 1.

δ _mixed = δ ₁ ψ ₁ + δ ₂ ψ ₂ Formula 1

In the formula: δ ₁ , δ ₂ represent the solubility parameters of the two pure solvents; ψ ₁ , ψ ₂ represent the volume fractions of the two pure solvents. Since the polymer cannot be vaporized, the determination of the solubility parameters of the polymer is cumbersome, such as swelling method, viscosity method, turbidity titration method, etc., and the error of the measurement result is relatively large.

Contents of the invention

The invention mainly aims at measuring the solubility parameter of the polymer, and proposes a new fluorescent probe method to measure the solubility parameter of the polymer.

The technical solution adopted in the present invention is: a method for measuring polymer solubility parameters by fluorescent probe method, the steps are as follows:

(1) Synthesis of small fluorescent probe molecules with functional groups,

In step (1), the fluorescent probe small molecules with functional groups are synthesized based on the following fluorescent molecules:

The functional groups are: -OH, -COOH, -NH ₂ , -COX, -COOR, -(CO) ₂ O-, -N=C=O, -CHO, -X (X is a halogen element), -C = C-,

Small fluorescent probe molecules with functional groups can be used as initiators to initiate polymerization of polymer monomers, monomers participating in polymer polymerization, and functional monomers grafted onto polymer molecular chains,

For example, the probe small molecule 4-hydroxytetraphenylethylene synthesized by the McMurry method has the equation:

Raw material formula: benzophenone (2.2g, 12mmol), 4-hydroxybenzophenone (1.9, 10mmol), zinc powder (2.9, 44mmol), titanium tetrachloride (TiCl ₄ , 2.4mL, 22mmol) solvent: Tetrahydrofuran (THF, 80 mL),

Then introduce the double bond into the 4-hydroxytetraphenylethylene obtained above, and react 4-hydroxytetraphenylethylene with acryloyl chloride to synthesize 4-acryloyloxytetraphenylethylene, the equation is:

Raw material formula: 4-hydroxytetraphenylethylene (0.1g, 0.3mmol), acryloyl chloride (0.03mL, 0.36mmol), triethylamine (Et ₃ N, 0.3mL) solvent: THF (4mL);

(2) Introducing the small probe molecules with functional groups synthesized in step (1) into the polymer molecular chain of the solubility parameter to be measured to obtain a copolymer,

In step (2), 4-acryloyloxytetraphenylethylene and methyl methacrylate are copolymerized, and fluorescent probe tetraphenylethylene groups are introduced into polymethyl methacrylate,

Polymerization formula: 4-acryloxytetraphenylethylene (0.03g), methyl methacrylate (1.5g), initiator: AIBN (0.01g), solvent: DMF (7.7g), reaction temperature: 70°C, reaction time : 16h;

(3) measure the fluorescence properties of the copolymer obtained in the step (2), and the fluorescence spectrum of the copolymer dissolved in different solubility parameter solvents, determine the solubility parameter of this polymer,

Dissolve the copolymer obtained in step (2) in THF/H ₂ O mixtures of different ratios (polymer concentration [C] = 1mg/mL), measure its fluorescence spectrum, and then add the copolymer to different solubility In the solvent of the parameter (polymer concentration [C]=1 mg/mL), detect the fluorescence spectrum (measured at room temperature (25° C.)), and obtain the solubility parameter of the polymer by comparing the fluorescence intensity.

The principle of measuring the solubility parameters of polymers is the principle of "similar compatibility", and when the solvent and the polymer are miscible, the solubility parameters of the two are similar: when the polymer is dissolved in its good solvent, the molecular chain is fully stretched, and at this time It is approximately considered that the solubility parameter of the polymer is equal to that of the solvent; when the polymer is in a poor solvent, its molecular chain is in a coiled state, and the solubility parameters of the two are not equal. The fluorescent probe method provided by the invention converts the stretched state of the microscopic polymer molecular chain into the macroscopic fluorescence intensity, so that we can determine the solubility parameter of the polymer. The introduced fluorescent probe molecules have no effect on the properties of the polymer, that is, the solubility parameter of the copolymer is equal to that of the polymer to be tested.

The solubility parameter range of polymethyl methacrylate measured by the present invention is 9.50cal ^1/2 cm ^{-3/2～ 10.00cal 1/2} cm ^-3/2 , and the range measured by comparative turbidity method is 8.60 cal ^1/2 cm ^-3/2～ 12.15cal ^1/2 cm ^-3/2 , comparing the results of the two, the results measured by the method for measuring polymer solubility parameters by the fluorescent probe method of the present invention are better than those measured by the nephelometric method The results obtained are narrower and more precise.

Description of drawings

Figure 1 is the ¹ H-NMR spectrum of 4-acryloyloxytetraphenylethylene synthesized in Example 1(2).

Fig. 2 is the fluorescence spectra of THF/H ₂ O mixtures in different ratios of the copolymer of 4-acryloyloxytetraphenylethylene and methyl methacrylate in Example 1 (3).

Fig. 3 is the fluorescence spectrum of the solution of the copolymer of 4-acryloyloxytetraphenylethylene and methyl methacrylate in Example 1 (3) with different solubility parameters.

Fig. 4 (a) is the transmittance and solubility parameter relation curve of ethanol titration polymethyl methacrylate by nephelometric titration;

(b) is the relationship curve between the transmittance and the solubility parameter of polymethyl methacrylate titrated with cyclohexane by nephelometric titration.

Detailed ways

Example 1

(1) 4-Hydroxybenzophenone (1.9g), benzophenone (2.2g), and zinc powder (2.9g) were added to a 250mL two-necked flask, vacuumed, filled with nitrogen for 3 times, and then added 80mLTHF, After cooling to 0°C, TiCl ₄ (2.4 mL) was added, and the mixture was refluxed overnight. After cooling to room temperature, add 80 mL of 1 mol/L hydrochloric acid, extract with dichloromethane, collect the organic phase and dry it with MgSO ₄ (anhydrous), evaporate the solvent to obtain a crude product, which is further separated and purified by a chromatographic column;

(2) Add the product (0.1g) in (1), 4mLTHF, and 0.3mL triethylamine into a 50mL two-necked flask equipped with magnetic stirring, and in an ice-water bath, drop 0.03mL acryloyl chloride into the reaction solution with a syringe, After more than 20 minutes, stir for 2 hours, evaporate THF, and separate and purify the product through a chromatographic column;

(3) The product (0.02g) in (2), methyl methacrylate (1.5g), azobisisobutyronitrile (0.01g), DMF (7.7g) were added to a 100mL three-necked flask, and an oil bath at 70°C Condensed and refluxed, reacted for 16h, the product was precipitated with methanol, and dried;

(4) The product in (3) is dissolved in the mixture of different ratios of THF/H ₂ O ([C]=1mg/mL), and the ultraviolet-visible light absorption spectrum is first performed to determine the excitation wavelength of the fluorescence spectrum (wavelength is 310nm), Measure its fluorescence spectrum again. Then dissolve in dichloromethane, cyclohexane, and ethanol in a mixed solvent with different solubility parameters ([C]=1mg/mL), and measure its fluorescence spectrum. determine its solubility parameters.

Analysis of the results of determination of polymer solubility parameters by fluorescent probe method

Figure 1 is the ¹ H-NMR spectrum of 4-acryloyloxytetraphenylethylene synthesized in Example 1(2).

¹ H NMR (400MHz, CDCl3, δ): 7.14-7.07(m, 9H), 7.05-6.99(m, 8H), 6.88(d, 1H), 6.55(d, 1H), 6.31-6.24(q, 1H ),5.99(d,1H),5.97(d,1H).

The number average molecular weight of the copolymer obtained in Example 1(3) was 16600, and the PDI was 1.64. The ultraviolet-visible light absorption spectrum determined that the excitation wavelength of the fluorescence spectrum was 310nm. Fig. 2 is the fluorescence spectrum of the THF/H ₂ O mixture of the copolymer of 4-acryloyloxytetraphenylethylene and methyl methacrylate in different proportions in Example 1,

It can be seen from Figure 2 that when the water content is 40%, the fluorescence intensity of the solution is weak, and as the water content in the solution increases, the fluorescence intensity of the solution also increases. This shows that the polymer synthesized in Example 1(3) has aggregation-induced luminescent effect. And with the increase of water content, each curve has the maximum value of fluorescence intensity at 465nm.

Fig. 3 is the fluorescence spectrum of the solution of the copolymer of 4-acryloyloxytetraphenylethylene and methyl methacrylate in Example 1 (3) with different solubility parameters.

It can be seen from Figure 3 that when the solubility parameter of the solvent ranges from 8.50cal ^1/2 cm ^-3/2 to 12.00cal ^1/2 cm ^-3/2 , the fluorescence intensity at a wavelength of 465nm first decreases and then increases. When the solubility parameters are at 9.50cal ^1/2 cm ^-3/2 and 10.00cal ^1/2 cm ^-3/2 , the fluorescence intensity is at the minimum. When the polymethyl methacrylate molecular chain is in its poor solvent, the molecular chain presents a coiled state, and at this time, the aggregation-induced luminescent effect groups on the polymethyl methacrylate molecular chain also gather together, and the fluorescence intensity is strong; When the polymethyl methacrylate molecular chain is in its good solvent, the molecular chain presents a stretched state. At this time, the aggregation-induced luminescent effect groups on the polymethyl methacrylate molecular chain are also dispersed, and the fluorescence intensity is weak. When the molecular chain is fully extended, the solubility parameter of the polymer is equal to the solubility parameter of the solvent, and because the content of the probe molecule is small, it is considered that the solubility parameter of the polymer is the same as that of the polymerized polymethyl ether under the same polymerization conditions. The solubility parameter of methyl acrylate is the same, and its range is 9.50～10.00cal ^1/2 cm ^-3/2 .

Comparative example 1

The solubility parameters of polymers were determined by turbidity titration, and the detailed steps were as follows:

Accurately weigh 25 ± 0.2 mg of the sample in Example 1 (3) and use dichloromethane as a solvent, fully dissolve it in a 25 mL clean volumetric flask ([C] = 1 mg/mL) at 50 ° C, cool to room temperature, and draw 5 mL of the solution in In a 50mL Erlenmeyer flask, titrate with ethanol and cyclohexane respectively, drop about 0.5mL each time, shake and mix well, take samples and wash the cuvette for 2 to 3 times, and finally take samples to measure the light transmittance. Its cloud point determines its sample solubility parameter.

Fig. 4 (a) is in comparative example 1, the transmittance and the solubility parameter relation curve of turbidity titration ethanol titration polymethyl methacrylate; (b) is in comparative example 1, turbidity titration cyclohexane The relationship curve between the transmittance and the solubility parameter of titrated polymethyl methacrylate.

It can be seen from Figure 4(a)(b) that the abrupt change point and cloud point of the light transmittance of the solution are at 8.60cal ^1/2 cm ^-3/2 and 12.15cal ^1/2 cm ^-3/2 respectively. Therefore, it is believed that the solubility parameter range of polymethyl methacrylate measured by turbidity method is 8.60cal ^1/2 cm ^-3/2～ 12.15cal ^1/2 cm ^-3/2 .

Claims (4)

1. a kind of method measuring polymer solubility parameters, it is characterised in that：Steps are as follows,

(1) the fluorescence probe small molecule of anamorphic zone functional group,

The probe small molecule 4- hydroxyl tetraphenyl ethylenes synthesized using Mcmurry methods,

Double bond is introduced on 4- hydroxyls tetraphenyl ethylene obtained above again, i.e., 4- hydroxyls tetraphenyl ethylene reacts synthesis with acryloyl chloride 4- acryloxy tetraphenyl ethylenes；

(2) polymer molecular chain that solubility parameters to be measured is introduced with the probe small molecule of functional group that will be synthesized in step (1) In, copolymer is obtained,

4- acryloxies tetraphenyl ethylene and methyl methacrylate are subjected to combined polymerization；

(3) fluorescence property of gained copolymer and the copolymer are dissolved in different solubility parameters solvents in determination step (2) Fluorescence spectrum, determine the solubility parameters of this polymer.

2. the method for measuring polymer solubility parameters as described in claim 1, it is characterised in that：In step (3), by step (2) copolymer of gained is dissolved in the THF/H of different ratio in₂In O mixtures, its fluorescence spectrum is surveyed；Copolymer is added to again In the solvent of different solubility parameters, detection fluorogram obtains the solubility parameters of polymer by the comparison to fluorescence intensity.

3. the method for measuring polymer solubility parameters as claimed in claim 2, it is characterised in that：In step (3), copolymer is molten In the THF/H of different ratio₂A concentration of 1mg/mL in O mixtures.

4. the method for measuring polymer solubility parameters as claimed in claim 2, it is characterised in that：In step (3), copolymer is molten A concentration of 1mg/mL in the solvent of different solubility parameters.