Preparation of Polymeric Conductive Materials by Solid-phase Sulfonation of Unsaturated Polyester Resin

1 Experimental part 1.1 Reagents and materials Unsaturated polyester, general purpose (commercially available); curing agent, general purpose (commercially available); 95% concentrated sulfuric acid, CP reagent, Sanming Sanyuan Chemical Reagent Factory; 50% fuming sulfuric acid , AR Reagent, Shanghai Zhenxing Chemical No.2 Plant; 1,2-Dichloroethane, AR Reagent, Shanghai Reagent No.1 Plant.

1mm; Polytetrafluoroethylene suspected pit (homemade): 7.5cmX 7cm (length x width x height), cut into 45 chamfers around.

1.2 Preparation of Unsaturated Polyester Resin Sheets Three parts of initiator, benzoyl peroxide, were mixed well and polymerized at room temperature. Unsaturated polyester resin does not volatilize during the curing process, can be molded at room temperature and pressure, has a high curing reaction capacity, and is easy to construct. Since the guanidine ring contains a certain number of benzene rings, the sulfonation reaction proceeds. Unsaturated polyester resins are susceptible to aging in oxidizing media such as nitric acid, concentrated sulphuric acid, and chromic acid. In particular, accelerated temperature aging accelerates corrosion resistance. The molded unsaturated polyester is hard, insoluble, and infusible, and has brown translucency.

Weigh 10g of unsaturated polyester and 0.1g of curing agent in a small beaker of 25mL, stir it evenly with a glass rod, and then slowly pour over 2 slides coated with silicone oil on the surface (use surface tension as much as possible without overflow) Fully-filled, exposed to air at room temperature, fully cured in about 1 d, and the unsaturated polyester sheet was peeled from the glass slide with a knife. Wash with water, dry, weigh, measure thickness.

1.3 Sulfonation The sulfuric acid is the mildest sulfonating agent used for the sulfonation of most aromatic compounds. Since the sulfonation reaction is a reversible reaction (for example, in the range of 100-200X: sulfonation of benzene, if the concentration of sulfuric acid used is low, the balance is close to 75%), an excessive amount of sulfonating agent is often used in order to increase the yield. Sulfonic acid is a relatively severe sulfonating agent that reacts with various aliphatic compounds. Sulfur trioxide is the most severe sulfonating agent, but it often produces by-products such as sulfur trioxide simulated solution or liquid sulfur trioxide solution, which can reduce the formation of by-products. Containing 5 fuming sulfuric acid can be sulfonated between 0 and 50 t. In this experiment, the following four sulfonation methods were used: the sheet was soaked in a 100-mL Erlenmeyer flask filled with 95% concentrated sulfuric acid at room temperature, stoppered with a rubber stopper, and removed after a certain time; according to the method, the ratio was 100:30. The volume ratio of the corresponding volume of 95% concentrated sulfuric acid and 50% fuming sulfuric acid were respectively mixed, and approximately 100% concentrated sulfuric acid was mixed and mixed as a sulfonating agent. The sheet was soaked in a 100-mL Erlenmeyer flask of 100% concentrated sulfuric acid at room temperature and stoppered. After a certain time, the sheet was removed; the sheet was first soaked in a 100-mL Erlenmeyer flask containing 1,2-dioxane. After it is fully swollen, the sheet is soaked in a 100-mL Erlenmeyer flask of 100% concentrated sulfuric acid at room temperature, and the stopper is plugged and removed after a certain time; 100% conical flask of concentrated sulfuric acid is heated in a 80X: silicone oil bath. At a constant temperature, the sheet is put into a spheronizing flask and removed after a certain period of time.

In the above four methods, the sheet is taken out from the sulfonating agent, first washed in a 50% sulfuric acid solution, then in a 25% sulfuric acid solution, and finally washed with water until the residual solution is titrated with a saturated BaCl 2 solution. When no white flocculent precipitate can be.

1.4 Properties of the polymer 1.4.1 Determination of the degree of sulfonation of the polymer After the sulfonated conductive polymer is cleaned, it is immersed in an Erlenmeyer flask containing a known volume of a dilute NaOH solution of known concentration (the solution must be able to After completely immersing the polymer, remove the sheet after about 24 hours. Rinse the dilute alkaline solution remaining on the surface of the sheet back into the conical flask bottle mother liquor with deionized water. Add 3 drops of phenolphthalein test solution to the mother liquor to make it red. Then titrate with 0.444 mol/L HCl solution until the mother liquor just changed from red to colorless, and note the amount of HC1 solution. Since the polymer sulfonated with a SO3H group, dilute NaOH solution can be used to displace H3 in a SO3H. By back-titration with HC1 solution, the amount of H+ in the conducting polymer can be calculated, that is, a quantity of SO3H. The degree of sulfonation of the polymer is then determined (characterized by the amount of a S03H group species carried by the unit weight of the conductive polymer).

1.4.2 Determination of Electrical Conductivity of Conductive Polymers The voltage and current values ​​are recorded and the conductivity data of the polymer can be obtained through a series of calculations.

Unit weight conductivity = current / (voltage x conductive polymer weight).

1.4.3 Determination of polymer sulfonation depth A series of conductive polymers of different sulfonation time are cut into pieces of the same size, the thickness of which is first measured by a vernier caliper and recorded, and then the upper and lower surfaces thereof are polished with fine sandpaper respectively. The conductivity was measured while grinding, until the conductivity of both the upper and lower surfaces was reduced to zero, and the thickness of the polymer was measured with a vernier caliper.

An SO 3 H group contained in the surface layer of the polymer gives the polymer a certain degree of electrical conductivity. Only when the sulfonated layer with a so3h group in the polymer is completely worn away, the thickness and the uncontaminated conductivity are zero. The difference in polymer thickness is the total thickness of the sulfonated layer corresponding to the sulfonation time of the conductive polymer, and one-half of that is the sulfonation depth corresponding to the sulfonation time.

2 experimental results The experimental process shows that when the unsaturated polyester resin is sulfonated in the sulfonating agent, the material is not easily eroded by concentrated sulfuric acid, but the sulfonation time cannot be too long, or it may easily cause excessive dissolution. For this experiment, the time should not exceed 2h. Considering the preparation and corrosion resistance of the sheet, the author chose unsaturated polyester resin as the material for preparing the conductive polymer.

2.1 Experimental results of the first sulfonation method Table 1 shows the experimental results of the unsaturated polyester resin sheet at 25C in 95% concentrated sulfuric acid. It can be seen from Table 1 that the unit weight conductivity of the sulfonated polymer is prolonged with time. While increasing, but due to the uneven curing and sulfonation, at 8.0,10.5h appeared inconsistent with the above rules; and the sample thickness decreased significantly with the sulfonation time. Considering conductivity and thickness factors comprehensively, the sulfonation time should not be exceeded. Table 1 Experimental results of unsaturated polyfluorene resin sheets in 95% concentrated decanoic acid 25t: sulfonation time/h voltage/V conductivity measurement current/fiA conductive polymerization Item Weight/g Unit Weight Conductivity 2.2 Second Sulfonation Method Test Results 4 md/LHC1 solution was back titrated and various measurements were performed. Unsaturated polyester resin sheets were sulfonated in 100% concentrated sulfuric acid, and the resulting unit weight conductivity increased significantly with the sulfonation time (see Table 2). Within 20 minutes of sulfonation, the unit weight conductivity has an upward jump with the sulfonation time.

Table 2 Experimental Results of Unsaturated Polyester Resin Sheets in 100% Concentrated Sulfuric Acid 25X: Determination of Sulfonated Conductivity Conductive Polymer Unit Weight HCl Solution Sulfonation Depth/mn Time/Voltage/Current/Conductivity/Weight /g Conductivity / Titration / Content / Polymer Non-conductivity Deuteration (mmohg1) Mill thickness at zero thickness Depth from Table 2 It can also be seen from Table 2 that the electrical conductivity per unit weight increases as the depth of sulfonation increases. When the sulfonation depth is zero, that is, there is no sulfonated layer, the conductivity per unit weight is also zero; the thicker the sulfonated layer, that is, the greater the sulfonation depth, the greater the conductivity per unit weight, which proves that the conductivity is indeed derived from the sulfonic acid group. Introduced. The sulfonation depth of the unsaturated polyester resin sheet increases with the extension of the sulfonation time, so the sulfonation of the resin by the concentrated sulfuric acid is penetrated from the outside to the inside and from the inside to the outside, and the longer the time, the more The deeper the agent penetrates, the thicker the sulfonated layer.

3 Conclusions The effect of sulfonation with concentrated sulfuric acid as the sulfonating agent is not obvious at room temperature. It takes a long time for sulfonation to obtain more conductivity, and obtaining a set of data takes more time than sulfonation with 100% concentrated sulfuric acid. Therefore, in this experiment, the author mainly prepared about 100% concentrated sulfuric acid as sulfonating agent.

The polymer sheet is sufficiently swelled in 1,2-dichloroethane and then sulfonated in about 100% concentrated sulfuric acid prepared. The resulting conductive polymer surface is rough, the sulfonation is not uniform, and the sulfonation time is Under the same conditions, the conductivity obtained by sulphonation after swelling is almost the same as the conductivity obtained by direct sulphonation without swelling, so the sulphonation reaction was performed directly in 100% concentrated sulfuric acid without swelling.

Unsaturated polyester resins have poor corrosion resistance in sulfonation agents. They are generally sulfonated in 100% concentrated sulfuric acid at room temperature. This results in higher conductivity in a shorter period of time and prevents excessive resin. Corrosion.