scispace - formally typeset
Search or ask a question
Topic

Kinetic chain length

About: Kinetic chain length is a research topic. Over the lifetime, 3020 publications have been published within this topic receiving 69160 citations.


Papers
More filters
Journal ArticleDOI

[...]

TL;DR: Atom transfer radical polymerization (ATRP) is one of the most successful methods to polymerize styrenes, (meth)acrylates and a variety of other monomers in a controlled fashion, yielding polymers with molecular weights predetermined by the ratio of the concentrations of consumed monomer to introduced initiator and with low polydispersities as discussed by the authors.
Abstract: Atom transfer radical polymerization (ATRP) is one of the most successful methods to polymerize styrenes, (meth)acrylates and a variety of other monomers in a controlled fashion, yielding polymers with molecular weights predetermined by the ratio of the concentrations of consumed monomer to introduced initiator and with low polydispersities. Because of its radical nature, ATRP is tolerant to many functionalities in monomers leading to polymers with functionalities along the chains. Moreover, the initiator used determines the end groups of the polymers. By using a functional initiator, functionalities such as vinyl, hydroxyl, epoxide, cyano and other groups have been incorporated at one chain end, while the other chain end remains an alkyl halide. The polymer can be dehalogenated in a one-pot process or the halogen end groups can be transformed to other functionalities using nucleophilic substitution reactions or electrophilic addition reactions. Moreover, utilizing the ability of the halogen chain end to be reactivated, radical addition reactions can be used to incorporate allyl end groups, insert one less reactive monomer unit at the chain end, or to end-cap the polymer chain. With ATRP, functionality and architecture can be combined resulting in multifunctional polymers of different compositions and shapes such as block copolymers, multiarmed stars or hyperbranched polymers.

1,148 citations

Journal ArticleDOI

[...]

TL;DR: In this article, a variety of different alkoxyamine structures led to α-hydrido derivatives based on a 2,2,5-trimethyl-4-phenyl-3-azahexane-3oxy, 1, skeleton which were able to control the polymerization of styrene, acrylate and acrylamide based monomers.
Abstract: Examination of novel alkoxyamines has demonstrated the pivotal role that the nitroxide plays in mediating the “living” or controlled polymerization of a wide range of vinyl monomers. Surveying a variety of different alkoxyamine structures led to α-hydrido derivatives based on a 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxy, 1, skeleton which were able to control the polymerization of styrene, acrylate, acrylamide, and acrylonitrile based monomers. For each monomer set, the molecular weight could be controlled from 1000 to 200 000 amu with polydispersities typically 1.05−1.15. Block and random copolymers based on combinations of the above monomers could also be prepared with similar control. In comparison with 2,2,6,6-tetramethylpiperidinoxy (TEMPO), these new systems represent a dramatic increase in the range of monomers that can be polymerized under controlled conditions and overcome many of the limitations associated with nitroxide-mediated “living” free radical procedures. Monomer selection and functional...

1,003 citations

Journal ArticleDOI

[...]

TL;DR: In this article, the kinetics of free radical reactions in isolated loci are discussed subject to the condition that the free radicals are supplied to the loci from an external source, and three cases of interest are considered: that the average number of free radicals per locus is small compared with unity, that this number approximates one half, and that the number is large.
Abstract: As a basis for understanding emulsion polymerization, the kinetics of free radical reactions in isolated loci is discussed subject to the condition that the free radicals are supplied to the loci from an external source. Three cases of interest are considered: that in which the average number of free radicals per locus is small compared with unity, that in which this number approximates one‐half, and that in which the number is large. Of these three possibilities, the second, in which the free radicals per locus approximate one‐half, is by far the most interesting as it explains in a satisfactory manner the characteristic features of styrene emulsion polymerization. For this case the average rate of reaction per locus is independent of the size of the locus, since this rate is simply one‐half the rate of polymerization of a single free radical. Thus the rate of emulsion polymerization, the concentration of monomer in the loci, and the number of loci present provide the information needed for calculating t...

896 citations

Journal ArticleDOI

[...]

TL;DR: In this article, a wide variety of unique polymer brush structures can be accomplished by "living" free radical polymerization of vinyl monomers from surface-tethered alkoxyamines or from tethered α-halo esters in the presence of (PPh3)2NiBr2.
Abstract: The preparation of a wide variety of unique polymer brush structures can be accomplished by “living” free radical polymerization of vinyl monomers from surface-tethered alkoxyamines or from tethered α-halo esters in the presence of (PPh3)2NiBr2. The use of a “living” free radical process permits the molecular weight and polydispersity of the covalently attached polymer chains to be accurately controlled while also allowing the formation of block copolymers by the sequential growth of monomers from the surface. These block and random copolymer brushes have been used to control surface properties.

856 citations

Journal ArticleDOI

[...]

TL;DR: In this article, a review of fundamental kinetic features of living radical polymerization (LRP) is presented, where the authors show that the product from LRP can have a low polydispersity, provided that the number of terminated chains is small compared to the number potentially active.
Abstract: This review covers fundamental kinetic features of living radical polymerization (LRP). Theories on polymerization rate R p and polydispersity index (PDI) and experimental investigations into individual LRP systems are summarized. The presence of bimolecular termination, which is unavoidable in LRP as well as in conventional radical polymerization, provides LRP with the characteristic time dependence of radical concentrations and hence R p and PDI, depending on experimental conditions, such as the presence or absence of conventional initiation. Despite the presence of termination (and initiation, in some cases), the product from LRP can have a low polydispersity, provided that the number of terminated chains is small compared to the number of potentially active, i.e. living, chains. On the premise that an activation–deactivation quasi-equilibrium holds, a large rate constant of activation, k act , is another fundamental requisite for low polydispersities. The kinetic parameters related to reversible activation reactions are tabulated. Treated in this review are nitroxide-mediated polymerization, atom transfer radical polymerization, iodide-mediated polymerization, reversible addition–fragmentation chain transfer polymerization, and organotellurium-mediated radical polymerization.

805 citations

Network Information
Related Topics (5)
Copolymer
84K papers, 1.2M citations
90% related
Polymerization
147.9K papers, 2.7M citations
88% related
Monomer
88.6K papers, 1.1M citations
85% related
Polymer
131.4K papers, 2.6M citations
84% related
Glass transition
40.7K papers, 1M citations
83% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20234
20223
20201
20186
201755
201653