What is a normal degree of polymerization?
The number-average degree of polymerization is a weighted mean of the degrees of polymerization of polymer species, weighted by the mole fractions (or the number of molecules) of the species. It is typically determined by measurements of the osmotic pressure of the polymer.
What is the difference between ATRP and RAFT?
The main difference of RAFT with ATRP is that RAFT is based on the transfer of activity between polymer chains bearing dithioester moieties and not on the reversible deactivation of growing polymer chains. Mostly dithiocarbonyl derivatives are used as chain transfer agents.
What is the degree of polymerization of polyethylene?
For example, polyethylene is composed of repeating units (CH2-CH2)n where “n” is an integer number that indicates the degree of polymerization. Mathematically, this parameter is a ratio of the molecular weights of the polymer and the respective monomer unit.
How does raft polymerisation work?
RAFT is a type of living polymerization involving a conventional radical polymerization which is mediated by a RAFT agent. Monomers must be capable of radical polymerization. There are a number of steps in a RAFT polymerization: initiation, pre-equilibrium, re-initiation, main equilibrium, propagation and termination.
What is RAFT chemistry?
RAFT (Reversible Addition Fragmentation chain Transfer) polymerization is a reversible deactivation radical polymerization (RDRP) and one of the more versatile methods for providing living characteristics to radical polymerization.
What is the degree of polymerization of polystyrene?
For example, polystyrene, with a degree of polymerization of n=7, is a viscous liquid. On the other hand, the commercial grade polystyrene is a solid with a degree of polymerization of n=1000. In addition, the degree of polymerization can be used to quantify the molecular length or size of a polymer.
What is the difference between HDPE and LDPE?
As its name suggests, low-density polyethylene (LDPE) has a lower density, strength, and temperature resistance. Meanwhile, high-density polyethylene (HDPE) is characterized by higher specific strength and heat resistance.
Who invented RAFT polymerization?
2.1 Reversible Addition-Fragmentation Chain Transfer Polymerization. RAFT polymerization, invented by Rizzardo, Moad, and Thang, is a facile and versatile CRP technique that is compatible with a wide range of monomers (acrylates, methacrylates, acrylamide, methacrylamide, styrene, and vinyl acetate).
Is RAFT living a polymerization?
How does RAFT polymerization work?
Reversible addition fragmentation chain-transfer polymerization (RAFT) is a controlled living radical polymerization that is associated with a series of reversible addition-fragmentation steps based on the degenerative chain transfer as a means of converting dormant chains to active propagating radical [120].
What are RAFT agents?
Commonly used RAFT agents include thiocarbonylthio compounds such as dithioesters,1 dithiocarbamates,4,5 trithiocarbonates,6 and xanthates,7 which mediate the polymerization via a reversible chain-transfer process.
What is degree of polymerization of cellulose?
The degree of polymerization of cellulose is calculated from the intrinsic viscosity of solutions prepared by dissolving cellulose in a suitable solvent, such as CED or cadoxen.
Why is LDPE weaker than HDPE?
HDPE has less branching in its polymer chains and has HDPE has stronger intermolecular forces. LDPE has more branching in its polymer chains; thus, it’s intermolecular forces are weaker.
Why is RAFT polymerization also count as controlled radicals?
RAFT is one of the most versatile methods of controlled radical polymerization because it is tolerant of a very wide range of functionality in the monomer and solvent, including aqueous solutions. RAFT polymerization has also been effectively carried out over a wide temperature range.
What is ATRP polymerization?
ATRP is a controlled radical polymerization process and is based on the reversible homolytic cleavage of the C–X bond of an alkyl halide or pseudohalide. Once again, the control of the polymerization is achieved by maintaining a low concentration of radicals throughout the polymerization.
Can ATRP control the formation of graft copolymers with well-defined polymer structures?
The use of ATRP techniques could control the formation of graft copolymers with well-defined polymer structures with various architectures such as block, graft, starlike, multiarmed, and hyperbranched polymers ( Xu et al., 2009 ), which help in understanding the structure–property relationships of the graft copolymer.
What is atom transfer radical addition polymerization (ATRAP)?
The polymerization from this method is called atom transfer radical addition polymerization ( ATRAP ). As the name implies, the atom transfer step is crucial in the reaction responsible for uniform polymer chain growth.
What are the mechanistic parameters of ATRP?
Understanding the Mechanistic Parameters ATRP: The Chemistry Fundamentals of an ATRP Reaction Atom Transfer Radical Polymerization ATRP in Protic Media Catalyst Development Structural Characterization of an ATRP Catalyst Complex