Method for preparing high molecular weight and segmented polymers by reversible addition-fragmentation chain transfer emulsion polymerization

Abstract

The invention discloses a method for preparing high molecular weight and segmented polymers by reversible addition-fragmentation chain transfer emulsion polymerization. The method comprises the following steps: adding 20 to 40 portions of water, 0.1 to 1.5 portions of an amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent and 1 to 20 portions of first monomer by weight into a reactor, and stirring and mixing the mixture; introducing nitrogen into the reactor; heating the reactor to a temperature of between 50 and 80 DEG C; adding 0.002 to 0.04 portion of water-soluble initiator by weight into the reactor; adding aqueous solution containing 0.01 to 2 portions of alkali by weight into the mixture while polymerization is initiated for 10 to 60 minutes; and keeping polymerization for 0.5 to 4 hours. The method has the advantages that the alkali is added afterwards, so the stability of the emulsion is improved, and high molecular weight polymers and segmented polymers can be synthesized; meanwhile, the method has simple flow equipment, low energy consumption, short reaction time, high final percent conversion, non additional conventional emulsifier, has actual molecular weight in accordance with a molecular weight design value and distribution of the molecular weight less than 2.5, and has good industrial prospect.

Description

technical field [0001] The invention relates to emulsion polymerization, in particular to a method for preparing high molecular weight and block polymers by reversible addition chain scission chain transfer emulsion polymerization. Background technique [0002] Compared with other traditional polymerization methods, emulsion polymerization has many advantages: the polymerization reaction occurs in the latex particles dispersed in the water phase. Although the viscosity inside the latex particles is high, since water is the continuous phase, the viscosity of the whole system is not high. The viscosity of the system does not change much during the entire reaction process, which makes the heat transfer of the entire system easy; due to the free radical isolation effect, high reaction rates and high molecular weight polymers can be achieved simultaneously in emulsion polymerization; most Emulsion polymerization uses water as the dispersion medium, which avoids the trouble of exp...

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Problems solved by technology

However, efficient reversible addition scission chain transfer emulsion polymerization of styrene has not been achieved in practice: Gilbert et al. 1，2 People use polymethacrylic acid-polybutylacrylate amphiphilic macromolecular reversible addition chain scission chain transfer reagent to feed emulsion polymerization with starvation method, the process is complicated and the obtained molecular weight deviates greatly from the molecular weight design value; Charleux et al. 3 In 2008, polyethylene oxide macromolecular reversible addition chain scission chain transfer reagent was used for batch emulsion polymerization of styrene, and the final conversion rate was only 66.7% at 22.7 hours; other amphiphilic macromolecular reversible addition chain scission chain transfer Reversible addition chain scission chain transfer reagent 4 , A single-block reversible addition chain scission chain transfer reagent of ethylamine polydiethylmethacrylate 5 , Two-block reversible addition of poly(ethylene oxide) poly(diethylmethacrylate) ethylamine to chain scission chain transfer reagent 6 Batch emulsion polymerization of styrene failed to show any control over molecular weight and molecular weight distribution

The main problem of the current failure is that other people's amphiphilic macromolecular reversible addition chain scission and chain transfer reagents must be dissolved in water by adding alkali due to the inappropriate length ratio of hydrophilic and lipophilic segments, forming an aqueous phase. The pH value of the solution is ≥5.5, the result of the polymerization reaction is that the molecular weight is out of control, the molecular weight distribution is wide, the reaction polymerization inhibition period is very long, the reaction speed is slow, the final conversion rate is low, the emulsion is unstable, and high molecular weight polymers cannot be synthesized well and block copolymers

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