RAFT Agent Lewis Base Moiety Block Copolymer Synthesis
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Solution Overview
Problem
Conventional RAFT polymerization methods face difficulties in preparing block copolymers from monomers with disparate reactivities, such as vinyl acetate and acrylate, due to the limitations of existing RAFT agents which are either unsuitable or unstable under certain conditions.
Innovation Solution
Development of RAFT agents with a Lewis base moiety covalently bound to O or N atoms, which form a Lewis adduct that allows for the control of polymerization of both less and more activated monomers, enabling the preparation of block copolymers through a multi-stage RAFT polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RAFT agents are used to polymerise monomers with disparate reactivities, then the polymerisation of less activated monomers can be controlled, but the polymerisation of more activated monomers cannot be controlled due to agent unsuitability
Solution Approach 1:
The invention changes the chemical parameters of the RAFT agent by introducing a Lewis base moiety that can form a Lewis adduct. This parameter change enables the agent to control polymerisation of both less activated and more activated monomers, resolving the contradiction between adaptability and reliability.
Solution Approach 2:
The Lewis adduct formed by the Lewis base moiety acts as an intermediary that mediates between the RAFT agent and monomers with disparate reactivities. This intermediary structure enables the single agent to effectively control polymerisation across different monomer activation levels.
2Manufacturing precision
If existing RAFT agents are used for monomers with markedly disparate reactivities, then some polymerisation control is achieved, but the molecular weight distribution becomes broad due to agent limitations
Solution Approach 1:
The modified RAFT agent with Lewis base moiety achieves multi-functionality by being able to control polymerisation of both less activated and more activated monomers. This universal capability maintains narrow molecular weight distribution across different monomer types, resolving the contradiction between manufacturing precision and adaptability.
3Adaptability or versatility
If conventional methods are used to prepare block copolymers from less activated and more activated monomers, then statistical copolymers can be formed, but block copolymers cannot be prepared due to reactivity differences
Solution Approach 1:
The invention changes the chemical parameters of the RAFT agent to enable sequential polymerisation of monomers with markedly disparate reactivities. This parameter modification allows precise control over block copolymer formation, resolving the contradiction between adaptability and manufacturing precision.
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 production of polymers with well-defined molecular architecture and narrow molecular weight distribution, overcoming the limitations of traditional RAFT agents by allowing the use of a single RAFT agent to polymerize monomers with markedly disparate reactivities, thus facilitating the synthesis of novel copolymers.
Implementation Method 1
RAFT agents with a Lewis base moiety covalently bound to O or N atoms, which form a Lewis adduct that allows for the control of polymerization
Implementation Method 2
Reversible addition-fragmentation chain transfer (RAFT) polymerisation, as described in International Patent Publication No. WO 98/01478, is a polymerisation technique that exhibits the characteristics associated with living polymerisation
Data Source
AI summary
A method of preparing polymer, the method comprising polymerizing one or more ethylenically unsaturated monomers of formula (I)where U is selected from H, C1-C4 alkyl or halogen; V is halogen or of the form O-G where G is selected from —C(O)R1 and —R1, or V is of the form NGGa where G is as defined above and Ga is selected from H and R1, G and Ga form together with N a heterocyclic ring, or V is of the form CH2Gb where Gb is selected from H, R1, OH, OR1, NR12, PR12, P(O)R12, P(OR1)2, SR1, SOR1, and SO2R1; and where the or each R1 is independently selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted arylalkyl, optionally substituted heteroarylalkyl, optionally substituted alkylaryl, optionally substituted alkylheteroaryl, and an optionally substituted polymer chain,under the control of a RAFT agent of formula (II) or (III),where Y is a Lewis base moiety and Y* is an n-valent Lewis base moiety; X is O or NR1, R1 is as defined above or forms together with Y or Y* and N a heterocyclic ring; m is an integer ≧1; n is an integer ≧2; and where R* is a m-valent radical leaving group that affords R*. which initiates free radical polymerization of the one or more ethylenically unsaturated monomers of formula (I), and R is a free radical leaving group that affords R. which initiates free radical polymerization of the one or more ethylenically unsaturated monomers of formula (I).