... If a molecule has ν branches, it has ν + 2 chain ends. Two limiting cases are combs
If the concentration of junction points is high enough, a point can be reached at which
the polymer molecule becomes a giant three dimensional network, and it is said to be
cross-linked. However, it is als ...
Chemistry 595: Physical Chemistry of Polymers
... topic, go to literature and learn about the current state of knowledge in that topic. Write a ~6-8
pages paper describing what you learned, formulating the major challenges and important
problems in this topic. You will also present a ~15 minutes talk on the material during the last
weeks of classes ...
Combustion and thermal degradation of polymers
... Depending on catalysts the chain growth in anionic polymerization can go through
two, three four or more directions not only in one direction as shown in the above
In cationic polymerization as catalysts are used Lewis acids and Friedel-Crafts
catalysts such as BF3, AlCl3, and SnCl4 and str ...
Controlled Fabrication of Cross-Linked Nanoparticles/Polymer
... this problem by suspending the silicon wafer in the diluted solution
under continuous stirring. Furthermore, the slow polymerization
rate in the solution kept the concentration of insoluble polymers
low in the whole synthetic fabrication of homogeneous, cross-linked
PLDMA films so that no polymers d ...
Surface Polymerisation (Polymer) 1 Plasma Enhanced Chemical
... higher concentration of polymerization building blocks than in the conventional
processes and initiation and chain termination reactions dominated here over chain
propagation. Moreover termination does not necessary interrupt the plasma
polymerization, since the neutrals formed in the termination st ...
EXPERIMENT 28 Intrinsic Viscosity: Chain Linkage in Polyvinyl
... For the determination of very high molecular weights, freezing-point
depressions, boiling-point elevations, and vapor-pressure lowerings are
too small for accurate measurement. Osmotic pressures are of a
convenient order of magnitude, but measurements are time-consuming.
The technique to be used in ...
... Addition or chain growth polymerisation is the linking of molecules having mul- tiple bonds.
These unsaturated monomers have extra internal bonds which are able to break and link up
with other monomers to form repeating chain. All the addition polymers are chain growth
polymers, but few examples of ...
Classification of polymers
... Gibbs free energy of mixing is
ΔG = ΔH - TΔS
The important points to be considered in thermodynamics of polymer
... Polymerized ionic liquids have excellent thermal resistance, high CO2 sorption capacities at low pressure,
fast reversible adsorption/desorption, and exceptional selectivity for CO2 over permanent gases. These
properties make pILs outstanding candidates as membrane separation layers for selective CO ...
The role of chain length and conformation in stress
... fracture plane. In thermoplastic solids, where chains cohere
through van der Waals forces, this involves several terms,
which all depend on the stress transfer through and the
breaking of secondary bonds. The relative contributions of
the different mechanisms are well reflected by the fracture
SYNTHESIS OF HIGH MOLECULAR WEIGHT POLY (METHYL
... Re-initiation: The radical produced from RAFT adduct propagates with the
monomer and form another reactive polymer chain.
Main-RAFT equilibrium: In an ideal situation, the radicals have the same
opportunity to propagate with the species, which have not been terminated
through a rapid exchange proces ...
Self-Assembly of Narrowly Distributed Carboxy
... swollen by the hydrophobic monomers presented in the
dispersion so that a further reaction inside these micelle-like nanostructures could lead to stable polymeric
latex particles. Therefore, it is important for us to
understand how these short polystyrene chains are selfassembled in water in the ini ...
Physical Chemistry of Polymers: Entropy
... 1.C. Recent Developments. Synthesis. Conventional polymerization methods, either of the step-growth (e.g., polycondensation) or chain-growth (e.g., free radical) class, produce
broad molecular weight distributions and offer little control over
long-chain architectural characteristics such as branchi ...
THE ROLE OF FeSO4 IN THE OBTAINING OF
... the grafted polymerization. Unreacted PVP may be
washed out during hydration that affects physicomechanical properties of copolymers. Therefore from the
scientific and practical points of view it is interesting to
determine the amount of reacted PVP. One can see from
Table 2 that copolymer compositi ...
Tuning the Molecular Properties of Polybenzimidazole by
... solubility of TPA in PPA being very low34 when the monomer
concentration is high (4.83 wt % in Table 1), more and more
TPA is precipitating out from the reaction mixture as insoluble
solid destroying the stoichiometric balance. This in turn
disfavors the reaction equilibrium and yields low IV polyme ...
... substances may be placed. Technologies for microencapsulating materials have been around for
several years, primarily for applications involving minimisation of hygroscopy and chemical
interactions, elimination of oxidation, and controlled release of nutraceuticals.
The Use of Man-Made Liposomes
Design of Thermoresponsive Polymers with
... respond only within a speciﬁc range of an environmental
variable rather than just beyond a critical value.
Reversible deactivation radical polymerization (RDRP)
techniques have been applied to produce block copolymers
comprising LCST- and UCST-type blocks in which the
diﬀerent parts of the macromole ...
In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to terminate has been removed. This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain propagation. The result is that the polymer chains grow at a more constant rate than seen in traditional chain polymerization and their lengths remain very similar (i.e. they have a very low polydispersity index). Living polymerization is a popular method for synthesizing block copolymers since the polymer can be synthesized in stages, each stage containing a different monomer. Additional advantages are predetermined molar mass and control over end-groups.Living polymerization is desirable because it offers precision and control in macromolecular synthesis. This is important since many of the novel/useful properties of polymers result from their microstructure and molecular weight. Since molecular weight and dispersity are less controlled in non-living polymerizations, this method is more desirable for materials designIn many cases, living polymerization reactions are confused or thought to be synonymous with controlled polymerizations. While these polymerization reactions are very similar, there is a distinct difference in the definitions of these two reactions. While living polymerizations are defined as polymerization reactions where termination or chain transfer is eliminated, controlled polymerization reactions are reactions where termination is suppressed, but not eliminated, through the introduction of a dormant state of the polymer. However, this distinction is still up for debate in the literature.The main living polymerization techniques are: Living anionic polymerization Living cationic polymerization Living ring-opening metathesis polymerization Living free radical polymerization Living chain-growth polycondensations↑ ↑ ↑ ↑ ↑