Preparation Of Macromolecular Surfactants And Study On Their Surface Applications

In recent years,the demand for surfactants has become increasingly diversified and high-performance,and in particular,the demand for macromolecular surfactants has increased.However,there are few types of macromolecular surfactants that can be used to meet the development needs of the times.Therefore,it is meaningful and promising to study the synthesis and performance of macromolecular surfactants.In this paper,two kinds of amphiphilic block polymers containing fluorine and fluorine-free were prepared by reversible fracture transfer radical polymerization.The relationship between the preparation conditions and the surface properties of the synthesized products and their surface properties were studied for the purpose to understanding further of the properties of molecular surfactants containing fluorine or not.The RAFT polymerization method was used in this paper to prepare the amphiphilic copolymerization by using acrylic acid?AA?as the hydrophilic monomer,while dodecafluoroheptyl methacrylate?DFMA?and lauryl methacrylate?LMA?as the hydrophobic monomers,respectively,to give copolymers PAA-b-PLMA and PAA-b-PDFMA.The properties of these surfactants were compared.Firstly,the preparation of two macromolecular surfactants was studied.A series of synthetic products were characterized by FTIR,1H NMR and GPC.The polymerization process was proved as an"active"reaction by studying the relationship between polymerization time and reaction conversion rate.The effect was discussed of the ratio of the monomer to chain transfer agent or to initiator on the molecular weight and on the molecular weight distribution of the polymerization product,respectively.It is proved that the molecular weight is controllable and the molecular weight distribution is narrow.The molecular size was calculated by worm-like chain model,in which the sizes of the fluorine-containing amphiphilic block copolymers are 60²00 nm²;and of the fluorine-free amphiphilic block copolymer are 50 and 600 nm².The HLB values were calculated by the molecular weight fraction method are 0.9¹2 of the fluorine-containing amphiphilic block copolymers,and 0.9¹6 of the fluorine-free amphiphilic block copolymers.However,because of the molecular fraction method,this value is high for fluorine-containing systems.Secondly,the surface performance parameters and the emulsifying properties of two macromolecular surfactants in water were compared.When the molecular weight of the macromolecular surfactant PAA-b-PDFMA is 0.86×10⁴ and the molecular weight of the hydrophobic segment is 1.45×10⁴,the CMC value is about 0.5×10^-4g/mL.The surface tension of water is reduced to 33.67 mN/m,which has the best emulsification effect on MMA in water.When the molecular weight of PDFMA in PAA-b-PDFMA raised to 3.11×10⁴,the static contact angle of water can reach to142.9o.The macromolecular surfactant PAA-b-PLMA has a molecular weight of 1.52×10⁴for the hydrophilic segment and a molecular weight of 1.32×10⁵for the hydrophobic segment,its CMC value is about 1.22×10^-55 g/mL.The surface tension of water can be reduced to 35.58 mN/m,which has the best emulsification effect on MMA in water.When the molecular weight of PLMA in PAA-b-PLMA raised to 3.00×10⁵,the static contact angle of water can reach to 113.3o.Both macromolecular surfactants represented a good antifoaming performance in aqueous solution,while the small molecule surfactant sodium dodecyl sulfate would produce a lot of foam and maintain its stability.This shows that the two macromolecular surfactants are superior to the small molecule surfactant in defoaming performance,which makes the foam stability decrease and is easily destroyed.It can be very useful for those required antifoaming or defoaming in coatings,food and other cases.Finally,we also explored the additional effects of two surfactants on corrosion resistance.By coating the tinplate,the protective properties of the two macromolecular surfactants on the iron tablets were observed.It was found that when the two macromolecular surfactants were used for coating,the tinplate pieces could be delayed in a short time,while could effectively extends the protect time when coated thereon the tinplate coated with epoxy resin.