Poly(N-vinyl lactam) Stabilisers for Hydrophobic Monomer Polymerisation
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Solution Overview
Problem
Current reactive stabilizers used in polymerization processes are limited to specific vinyl monomers, such as alkyl methacrylate and acrylate, and are not suitable for a wide range of hydrophobic monomers, including vinyl esters and N-vinyl monomers, which restricts their application in polymerization processes.
Innovation Solution
The use of a new type of reactive stabilizer, a living polymer chain resulting from controlled radical polymerization of N-(vinyl lactam) monomers with a thiocarbonylthio group, which can stabilize the dispersed phase and control polymerization in an aqueous medium, allowing for the polymerization of various hydrophobic monomers like vinyl esters and N-vinyl monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional reactive stabilizers are used, then polymerization of specific vinyl monomers (alkyl methacrylate and acrylate) is achieved, but the application range is restricted and cannot polymerize vinyl esters and N-vinyl monomers
Solution Approach 1:
The patent develops a universal reactive stabilizer based on poly(N-vinyl lactam) that can polymerize multiple types of hydrophobic monomers including vinyl esters, N-vinyl monomers, and alkyl methacrylates through a common mechanism involving thiocarbonylthio groups, eliminating the need for different stabilizers for different monomer classes
Solution Approach 2:
The invention changes the chemical structure parameters of the reactive stabilizer by using poly(N-vinyl lactam) with specific thiocarbonylthio end groups, which alters the polymerization mechanism to accommodate a broader range of monomers while maintaining controlled radical polymerization through RAFT or MADIX processes
2Stability of the object's composition
If additional surfactants are used to stabilize the dispersed phase, then emulsion stability is improved, but the polymer dispersion contains unwanted surfactant residues
Solution Approach 1:
The reactive stabilizer performs dual functions: it stabilizes the dispersed phase through its hydrophilic poly(N-vinyl lactam) chain while simultaneously participating in the polymerization reaction as a control agent, eliminating the need for separate surfactant additives and producing surfactant-free polymer dispersions
Solution Approach 2:
The invention merges the functions of emulsion stabilizer and polymerization control agent into a single molecule - the reactive stabilizer with poly(N-vinyl lactam) chain and thiocarbonylthio group, which simultaneously provides steric stabilization and controlled radical polymerization capabilities
3Productivity
If polymerization temperature is increased to improve reaction rate, then productivity is improved, but the thiocarbonylthio group degrades
Solution Approach 1:
The invention changes the temperature parameter to below 40°C (preferably 0-30°C) to preserve the thiocarbonylthio group integrity, and compensates for the reduced reaction rate by using redox initiator systems that generate radicals at lower temperatures, maintaining both productivity and group stability
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 polymerization of a broad range of hydrophobic monomers, including vinyl esters and N-vinyl monomers, resulting in stable polymer dispersions with controlled particle size and reduced surfactant content, suitable for producing surfactant-free or low-surfactant latexes, such as fluorinated polyolefins.
Implementation Method 1
they ensure the role of polymerization control agent, typically by processes of reversible transfer by addition-fragmentation, whereby the polymer chains grow from this control agent by progressive consumption of the monomers contained in each
Implementation Method 2
The source of free radicals used in step (E1) is preferably a redox-type polymerization initiator
Data Source
Figure 1
AI summary
The present invention concerns a method for preparing a polymer comprising a step (E1) for dispersed phase polymerisation in the presence of a reactive stabiliser, wherein the following are brought into contact in an aqueous phase: - at least one ethylenically unsaturated monomer; - at least one source of free radicals; and - a reactive stabiliser comprising a polymer chain including monomer units (N-vinyl lactam) and a thiocarbonylthio-S group (C=S)-.