Synthesis And Application Of Novel Sugar-based Nonionic Surfactant

Sugar-based nonionic surfactants are a class of green chemicals with excellent performance.In this paper,a series of N-alkyl lactobionic acid amide surfactants with single alkyl length and single-head groups were prepared from the third-generation advanced fructose lactobionic acid（LBA）through amide bonds with series of fatty amines.Their aggregation behavior and surface properties in aqueous solution were discussed.For the first time,this kind of green surfactant was applied to the modification of core-shell polyacrylate（PA）emulsion,and the functional monomer hydroxyethyl methacrylate（HEMA）was innovatively added to the core layer structure and acrylic acid（AA）was added to the shell structure.Molecular design of core-shell PA was carried out to realize the composite modification of PA by compound emulsifier and core-shell structure.The main investigations and results of the paper are as follows:Using a two-step method,LBA was used as the raw material to synthesize lactonolactone,which was then reacted with alkylamines with different lengths of carbon chain(C₈H₁₇NH₂,C₁₂H₂₅NH₂,C₁₄H₂₉NH₂ and C₁₈H₃₇NH₂)to generate the target products a₁～a₄.In the first step,the product yield reached 87.6%under the optimal process conditions.The optimal process conditions in the second step were:n（lactolactone）:n（alkylamine）=1:1.2,the solvent was anhydrous methanol,the reaction temperature was 60°C,and the reaction time was 6 h.Under the optimum process conditions,the respective yields of a₁～a₄ were:a₁:83.6%,a₂:76.7%,a₃:71.0%,a₄:61.7%.The structure of the product was characterized by Fourier transform infrared spectroscopy（FTIR）and nuclear magnetic resonance spectroscopy（¹H NMR）,and the experimental results were found to be consistent with the expected.The products were characterized and analyzed by surface tensiometer,dynamic light scattering（DLS）technology,contact angle test and transmission electron microscope（TEM）.At 25℃,the critical micelle concentrations（CMC）of a₁～a₄ were:1.40×10^-2 mol·L^-1,3.31×10^-4 mol·L^-1,1.26×10^-4 mol·L^-1and 2.51×10^-5 mol·L^-1respectively.The corresponding critical surface tensions were:31.8 m N·m^-1,37.2m N·m^-1,40.4 m N·m^-1 and 43.2 m N·m^-1.The aggregation behavior of each product in different concentrations of aqueous solution was different,and there were multiple aggregated forms such as spherical micelles,vesicles and sponge-like aggregates.The particle size was mainly distributed in three following ranges:1～10 nm,10～100 nm and 100～1000 nm.In a certain concentration range,with the increase of concentration,the aggregation state of small particle size became increased,and with the increase of alkyl carbon chain,the aggregation state of large particle size also became increased.In this paper,styrene（ST）was used as the hard monomer,butyl acrylate（BA）was used as the soft monomer,HEMA and AA were used as functional monomers,and ammonium persulfate（APS）was used as the initiator.The method of semi-continuous seed emulsion polymerization was adopted.To synthesize core-shell PA emulsion,the mass ratio of core-shell was fixed at 1:1,and the reaction temperature,stirring rate and other conditions were kept constant.OP-10 was replaced by a₁～a₄ to help keeping the emulsion stable.By FTIR,gel permeation chromatography（GPC）,differential scanning calorimetry（DSC）,comprehensive mechanical property tester and other instruments,the effects of the ratio of soft and hard monomers in core-shell system on the comprehensive properties of emulsions and latex films and the changes of effects and performance before and after emulsifier modification were investigated.As the content of the core layer monomer and the shell layer monomer became closer,the average particle size of the core-shell PA emulsion was smaller.The addition of the modified emulsifier further reduces the average particle size.With the hardening of the core structure and the softening of the shell structure,the elongation at break of the latex film gradually increased,from 63%to 234%,and the tensile strength first increased and then decreased,up to 10.6MPa.Both the mechanical properties and thermal stability of the core-shell PA latex membranes modified by a₂ and a₃ were improved.