Block Copolymer Synthesis via Alpha-Methylstyrene Capping
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Solution Overview
Problem
Current methods for producing block copolymers of styrene and alkyl (meth)acrylates via living anionic polymerization face challenges, including the use of expensive and unsuitable diphenylethylene, wide molecular weight distribution, and incomplete block formation due to alternating reactions and inhibition by polar groups like carboxyl groups.
Innovation Solution
The method involves using α-methylstyrene instead of diphenylethylene for living anionic polymerization in a microreactor, allowing for the production of block copolymers with controlled molecular weight and narrow distribution by leveraging the difference in reaction rates between styrene and α-methylstyrene, and incorporating (meth)acrylates with functional groups that can be converted to polar groups post-polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diphenylethylene is used to cap the propagation end in living anionic polymerization, then block copolymer formation is achieved, but the reaction rate is too high causing alternating reaction with styrene instead of proper capping
Solution Approach 1:
The invention changes the chemical structure parameter of the capping agent from diphenylethylene to compounds with electron-withdrawing groups (such as esters, amides, or nitriles). This parameter change reduces the reaction rate of the capping agent with the propagation end, allowing it to cap the active end properly without causing alternating reaction with styrene, thus resolving the contradiction between reliability of block copolymer formation and reaction rate control
2Reliability
If diphenylethylene is used for capping, then block copolymer can be produced, but the cost is high making it unsuitable for industrial use
Solution Approach 1:
The invention replaces the expensive diphenylethylene with cheaper compounds containing electron-withdrawing groups such as esters, amides, or nitriles. These cheaper capping agents perform the same function of capping the propagation end to enable block copolymer formation, thereby reducing production cost while maintaining reliability for industrial use
3Adaptability or versatility
If living radical polymerization is used to produce block copolymer with polar groups, then polar groups can be incorporated, but wide molecular weight distribution and random copolymerization occur
Solution Approach 1:
The invention substitutes the living radical polymerization mechanism with living anionic polymerization mechanism. This mechanism substitution allows for better control over molecular weight distribution and prevents random copolymerization between styrene and polar monomers, while still enabling the incorporation of polar groups through the use of appropriate capping agents and polymerization conditions
4Adaptability or versatility
If carboxyl group containing monomer is used in living anionic polymerization, then polar group can be incorporated, but the carboxyl group inhibits polymerization
Solution Approach 1:
The invention applies preliminary protection to the carboxyl group by using esters, amides, or nitriles as capping agents before polymerization. This preliminary action prevents the carboxyl group from inhibiting the polymerization reaction during the living anionic polymerization process, while still allowing for the incorporation of polar groups. The protected form can be converted to the free carboxyl group after polymerization if needed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the industrial production of block copolymers without diphenylethylene, achieving narrow molecular weight distribution and reduced random copolymerization, while allowing for the incorporation of polar groups with minimal random copolymerization, thus overcoming previous limitations.
Implementation Method 1
subjecting a mixture of styrene or a derivative thereof and α-methylstyrene to living anionic polymerization in the presence of a polymerization initiator
Implementation Method 2
using a microreactor having a channel being capable of mixing a plurality of liquids with each other
Implementation Method 3
the polymer unit (B) derived from α-methylstyrene in the intermediate polymer serves as a propagation end to form a polymer block (C) derived from the (meth)acrylate compound
Data Source
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Figure 5~6
AI summary
The present invention provides a method for producing a block copolymer, which includes subjecting styrene or a derivative thereof (excluding α-methylstyrene) to living anionic polymerization in the presence of a polymerization initiator by means of a microreactor having a channel being capable of mixing a plurality of liquids with each other, reacting a propagation end of the resultant polymer block (A) derived from styrene or a derivative thereof with α-methylstyrene to obtain an intermediate polymer having a polymer unit (B) derived from α-methylstyrene bonded to one end of the polymer block (A), and then subjecting a (meth)acrylate compound (c) to living anionic polymerization in the presence of a polymerization initiator so that the polymer unit (B) derived from α-methylstyrene in the intermediate polymer serves as a propagation end to form a polymer block (C) derived from the (meth)acrylate compound (c).