Gemini Surfactant Mediated Hipe Template For Preparation Of Porous Material

High internal phase emulsion(HIPE)template method is a simple and efficient method for preparing porous polymers by polymerizing continuous phase and removing internal phase.Many factors will affect the structure of porous polymer including internal phase volume fraction,stirring speed,monomer properties,etc.The stabilizer of HIPE is one of the key factors.At present,the commonly used stabilizers are traditional surfactants or nanoparticles.However,several problems such as using a large amount of stabilizers,removing hardly and“closed-cell”pore structure,hamper the end application.As a new type of emulsifier,Gemini surfactants include a couple of hydrophilic groups and hydrophobic groups,respectively.Besides,Gemini surfactants will be More closely aligned,because the existence of spacers is conducive to and against electrostatic repulsion.Gemini surfactants could apply to HIPE as a new high efficiency stabilizer,due to their high performance like low critical micelle concentration(CMC)and good emulsification.This paper mainly studied the preparation of porous materials via HIPE template stabilized by carboxylate type Gemini surfactants,including main contents as following.1.A series of symmetrical carboxylate Gemini surfactants were synthesized(C_nNS-SNC_n,n=8,10,12,14).The effects of alkyl chain length on CMC,micelle size and emulsification performance were researched.Increasing the chain length caused the CMC value and solubility of Gemini surfactants decreased.However,it had a little influence on the size of micelles.Gemini surfactants exhibited good emulsification at low concentrations(30 mmol/L).which may be attributed to tight alignment of Gemini surfactants.Except the Gemini surfactant with the shortest alkyl chain(n=8),others can be used as stabilizer of HIPE to preparation porous polyacrylamide.And the diameter of macroporous decreased with the increase of alkyl chain.2.Gemini surfactant was used to stabilize HIPE template for the preparation of highly porous monolithic chitosan-g-polyacrylamide.The influence of dispersion phase and Gemini concentration on polymer pore structure were researched.Comparing with same molar concentration of tween-20,the polymer stabilized by Gemini surfactant exhibited larger size of pore and window.The pore diameter increased with increasing Gemini surfactant concentration and dispersed phase volume.The porous polymers showed an excellent ability to adsorb methylene blue.The maximun adsorption capacity was up to 487 mg/g in the present study.The adsorption process was in accordance with pseudo-secondary kinetic model,with a theoretical adsorption capacity up to 500 mg/g.Furthermore,the adsorption process was in accordance with Langmuir isotherm,illustrating that the adsorption occurred on monolayer.The thermodynamic studies show that adsorption can occur spontaneously at room temperature(20-40~oC),which belongs to physical adsorption.3.Three surfactants were used to stabilize high internal emulsion template for the preparation of hierarchically porous carbons.It was found that the type of emulsifier had a significant effect on the pore structure.The porous carbon prepared by Gemini emulsifier SDLC showed an“open-cell”structure,while the porous carbons prepared by Tween-20 and CTAB exhibited“closed-cell”structure.The increase of Gemini dosage was conducive to the increase of specific surface area of carbon materials,which could reach 466.8 m~2/g.The open-cell structure is beneficial to enhance the electrochemical properties.The carbon materials showed maximun capacitance of 165.5 F/g at 1 A/g.