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The homogeneous atom transfer radical polymerization of methyl methacrylate mediated by CuBr/N-(n-hexyl)-2-pyridylmethanimine was successfully carried out using an automated synthesizer. The effects of initiators, solvents and reactant ratios on the polymerization were investigated. Three different kinds of initiators, namely ethyl 2-bromoisobutyrate, (1-bromoethyl)-benzene, and p-toluenesulfonyl chloride, were utilized to initiate the polymerization and ethyl 2-bromoisobutyrate was proven to be the best initiator for the studied system in terms of molecular weight control and narrow polydispersities of the obtained polymers. The solvents used (i.e., toluene, p-xylene, and n-butylbenzene) were found to have strong effects on the polymerization. The reactions in toluene and p-xylene were well-controlled and almost the same polymerization rates were observed. However, the reaction rate dramatically increased in the case of n-butylbenzene, resulting in radical termination during the polymerization. The initiator and Cu(I) concentrations had a positive effect on the polymerization rate. In the meantime, all the reactions were controlled and polymers with predetermined molecular weights and low polydispersity indices (

Metal complexes based on different substituted dimethyl-2,2'-bipyridines and 5,5"-dimethyl-2,2':6',2"-terpyridine were used in combination with aluminium isopropoxide for the controlled radical polymerization of styrene, acrylate and methacrylate derivatives. Depending on the substitution pattern and the central metal ion the effectivity of the systems revealed distinct differences. The control over molecular weight, molecular weight distribution and reaction rate depends strongly on the choice of central metal ion and the ligand system. Best results concerning control of molecular weight and molecular weight distribution for styrene and acrylates were obtained using a combination of [Cu(II)(4,4'-dimethyl-2,2'-bipyridine)3](PF6)2, aluminium isopropoxide, (1-bromoethyl)benzene as initiator and acetonitrile as solvent at 75°C. Furthermore, the polymers obtained were colorless with a very low content of residual metal ions. Using this polymerization system, defined block copolymers and other special architectures are accessible.

With the increasing demand for industrial product quality improvement and production rationalization, the vibrational spectroscopic techniques of Raman, infra-red (IR), and near-infrared (NIR) spectroscopy have – in combination with light-fiber optics, new in-line and on-line probes, chemometric evaluation procedures, and imaging accessories – proved of value as extremely powerful tools for academic and industrial polymer research, quality control and reaction as well as process monitoring. Polymers have become an integral part of our everyday life and this chapter will demonstrate that Raman, IR, and NIR spectroscopy are extremely important characterization and control tools for the whole life cycle of a polymeric product. Apart from an introduction to the theoretical, instrumental, and experimental fundamentals of vibrational spectroscopy, the principal aim of this chapter is to demonstrate to the reader with the help of selected examples the broad range of applicability of the three techniques and encourage him to fully exploit their potential for the characterization of the chemical and physical properties of polymers.

Spontaneous degradation of bottlebrush macromolecules on aqueous substrates was monitored by atomic force microscopy. Scission of C─C covalent bonds in the brush backbone occurred due to steric repulsion between the adsorbed side chains, which generated bond tension on the order of several nano-Newtons. Unlike conventional chemical reactions, the rate of bond scission was shown to decrease with temperature. This apparent anti-Arrhenius behavior was caused by a decrease in the surface energy of the underlying substrate upon heating, which results in a corresponding decrease of bond tension in the adsorbed macromolecules. Even though the tension dropped minimally from 2.16 to 1.89 nN, this was sufficient to overpower the increase in the thermal energy (kBT) in the Arrhenius equation. The rate constant of the bond-scission reaction was measured as a function of temperature and surface energy. Fitting the experimental data by a perturbed Morse potential V = V0(1 - e-βx)2 - fx, we determined the depth and width of the potential to be V0 = 141 ± 19 kJ/mol and β-1 = 0.18 ± 0.03 Å, respectively. Whereas the V0 value is in reasonable agreement with the activation energy Ea = 80–220 kJ/mol of mechanical and thermal degradation of organic polymers, it is significantly lower than the dissociation energy of a C─C bond De = 350 kJ/mol. Moreover, the force constant Kx = 2β2V0 = 1.45 ± 0.36 kN/m of a strained bottlebrush along its backbone is markedly larger than the force constant of a C─C bond Kl = 0.44 kN/m, which is attributed to additional stiffness due to deformation of the side chains.

End-linked, degradable, amphiphilic polymer conetworks (APCNs) of various compositions and architectures were synthesized by sequential atom transfer radical terpolymerization of monomers and cross-linker using a cleavable, bifunctional initiator, bearing two acid-labile hemiacetal ester groups. The incorporation of the initiator residue into the conetworks rendered them cleavable in the middle of their elastic polymer chains. The temporal evolution of the swollen mass of the conetworks in acidified THF-water mixtures was studied and it was determined that the APCN hydrolysis rates were dependent on both conetwork composition and architecture. Regarding the former, hydrophobic APCNs degraded slowly or they even did not dissolve at all. Regarding the latter, conetworks with hydrophobic monomer and hydrophobic cross-linker units distributed around the initiator fragment also dissolved more slowly or they did not degrade at all. Finally, characterization of the star copolymers, produced from conetwork hydrolysis, allowed the determination of the APCN core functionality to be around 30. 3 1 105 116 Cited By :25

In this chapter the relevant phenomena that dominate the mechanical performance of polymer glasses are discussed. Mechanical properties as measured in short-term experiments are directly linked to their long-term performance. The molecular processes that are of influence are investigated. The chapter is divided into two sections: The first deals with the phenomenology of the deformation, and the second addresses the constitutive modeling and precise characterization of polymers, needed to model their mechanical response.

This chapter presents a comprehensive overview of the chemistry, process technology, and thermal and mechanical properties of hydrolytically prepared fully aliphatic and semiaromatic commercial polyamides (PAs). In addition, commercially available block copolyetheramides and the most important PA blends are discussed. A few molecular characterization methods, typically used for the characterization of PAs, are briefly discussed, as well as some physical phenomena very characteristic of PAs, such as the Brill transition and the odd–even effect in the melting points of a series of PAs. The applications of the wide variety of commercial PAs are discussed in terms of their properties.

Conetworks based on end-linked homopolymers and amphophilic gradient copolymers were synthesized by the atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methaerylate (DMAEMA, hydrophilic monomer), methyl methaerylate (MMA, hydrophobic monomer), and ethylene glycol dimethacrylate (EGDMA, hydrophobic cross-linker). Sequential, rather than step-wise polymerizations, were performed to enhance the livingness of the polymerization, particularly for the end-linking step, and to ultimately obtain conetworks based on gradient rather than pure block copolymers. Amphiphilic conetworks based on end-linked MMA-DMAEMA-MMA gradient copolymers of different compositions were successfully synthesized as confirmed by the narrow molecular weight distributions of the linear precursors, the rigidity of the amphiphilic conetwork products and the low sol-fraction extracted from the conetworks. Similarly successful was the ATRP synthesis of an end-linked conetwork based on a DMAEMA-MMA statistical copolymer and of a randomly cross-linked conetwork that resulted from the simultaneous terpolymerization of DMAEMA, MMA and EGDMA. An amphiphilic conetwork based on an end-linked DMAEMA-MMA-DMAEMA gradient copolymer presented a less rigid, mucous-like, texture. The degrees of swelling (DS) in tetrahydrofuran of all the conetworks were higher than those measured in pure water, whereas the aqueous DS values increased by lowering the pH and increasing the DMAEMA content of the conetworks. © 2010 Wiley Periodicals, Inc. 48 9 1878 1886 Cited By :20

The effect of nanoscale confinement on the dynamics of,I series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octidecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated with dielectric spectroscopy as a function of temperature and pressure. The main effects of confinement were found in the triblocks with the more antisymmetric compositions when the radius of gyration of the confined block was comparable to the cylinder radius. It was found that the dynamics of the amorphous block accelerate upon confinement. Furthermore, confinement of the crystallizable block within cylindrical nanodomains results in the depression of the crystallization temperature. Macromolecules

Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n-butyl acrylate (BA) has been investigated using 13C NMR measurements of branching in the poly(n-butyl acrylate) produced. The mol-% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short-chain radicals which can be expected to undergo both intra- and inter-molecular CTP at much higher rates than long-chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short-chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short-chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization.

The phase state of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated in bulk and on surfaces using small-angle X-ray scattering and atomic force microscopy, respectively. The mean-field theory was employed to construct the bulk phase diagram. Excellent agreement was found between the bulk and surface morphologies as well as for the domain spacing (domain spacing scaled as d approximate to N-0.64), suggesting that the strong polymer-polymer interactions in bulk are also the dominant interactions on surfaces. Langmuir

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Atom transfer radical polymerization of styrene and butyl acrylate has been investigated from a kinetic point of view. Attention is focused on the activation of the dormant species as well as on the termination that plays a role in these reactions. It has been shown that the activation of a styrene dormant species is much slower in methyl methacrylate compared to reported data obtained in styrene. Termination reactions seem to play a minor role in ATRP, although in the early stages of the reaction loss of functionality is observed. The reactivity ratios for the copolymerization of styrene and butyl acrylate are determined as well and are very similar to the ones for conventional free-radical polymerization. From simulations it is clear that the system is self-tuning in the sense that a difference in equilibrium constants between both dormant species does not lead to a change in radical ratios in the reaction mixture.