Functionalised monomers

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

The continuous and batch microwave reactors have been particularly useful for heating reactions in which thermally labile products are formed. For example, alkyl 2-(hydroxymethyl)acrylates have considerable potential as functionalised monomers and synthons128. Published syntheses at ambient temperature, however, required several days and were not conducive to scale-up129-133. The microwave procedure involved a modified Baylis-Hillman reaction, in which the parent acrylate derivative was reacted with formalin in the presence of 1,4-diazabicyclo [2.2.2] octane (DABCO). Preparations from starting acrylates, including methyl, ethyl and n-butyl esters, were easily achieved within minutes with multiple passes through the CMR, at ca. 160-180°C (Scheme 9.16). Rapid cooling was required to limit hydrolysis, dimerisation and polymerisation. Yields... 

In the first step, the contact occurring between the functionalised monomers and the template molecule leads to the formation of a complex. Its structure and stability will then determine the behaviour of the future MIR The interactions involved must be sufficiently strong to remain intact during the polymerisation stage but sufficiently labile to enable template extraction and reinsertion of guest molecules in the later stages. These interactions must therefore occur rapidly and be reversible. It is crucial to optimise the choice of the different components of the system at this point. 

Covalent interactions (Fig. 7) this approach involves the formation of an easily cleavable functionalised monomer-template complex [61, 18]. The first example of an imprinted polymer network was prepared by Wulff s group and used the reversible formation of an ester bond between a diol and 4-vinylphenylboronic acid [15]. The reaction rates to reach equilibrium between the ester and boronic acid are comparable to those obtained with... 

Fig. 8 Functionalised monomer/template molecule complexes based on strong non-covalent interactions (the various molecules are added in stoichiometric proportions) (1) adapted from [59] (2) adapted from [86]...

Direct measurement of the interaction between the network and the guest molecule, when it is possible to quantify the variations of a property depending on these interactions. For instance, the introduction of fluorescent probes, either via the functionalised monomer or via the guest would allow accurate assessment of any change in the immediate environment of the probes [ 136]. The use of MIPs as recognition elements in sensors led to the development of this approach (see below). 

The first polyacrylamide resins were synthesised by copolymerisation of /V,N-dimethylacrylamide 1 (basic monomer), ethylenebisacrylamide 2 (crosslinking agent) and N-acryloyl-N -(tert-butoxycarbonyl-P-alanyl)hexamethylene diamine 3 (functionalised monomer)H as shown in Scheme 1.5.5.1. 

Work has been performed in which the quaternary pyridinium functionality was attached to 7-oxanorbornene-5,6-exo-dicarboximide-functionalised monomers which were subsequently polymerised using a Grubbs catalyst (Grubbs catalysts are a series of transition metal carbene complexes used as catalysts for olefin metathesis). The polymer series, a-f, and quaternised polymer, a , (Figure 9.1 and Table 9.1) was designed to study the effect of the hydrophobic alkyl substituent on the antibacterial and haemolytic activities of polymers using dimethylformamide (DMF) as the solvent. 

The first requirement for this study was to make well-defined functionalised monomers for the synthesis of water-soluble or amphiphilic functionalised polymers. Such monomers are relatively easily obtained via Diels-Alder chemistry and a few examples of the genre are shown below. The raw materials required are a source of cyclopentadiene (1) and suitably functionalised dienophiles. Our first line of approach... 

Figure 1. ROMP polymerisable functionalised monomers carrying functional groups at the end of spacer units.

Further examples of the living polymerisation of ester functionalised monomers using the Schrock initiator are also reported. 

The development of well-defined ROMP initiators has expanded the scope of the metathesis reaction, permitting the controlled polymerisation of highly functionalised monomers. Schrock s well-defined olefin metathesis initiators became available in the mid 1980s and they were based on alkoxy imido complexes of tungsten and molybdenum of general... 

Monodisperse latex particles with surface amino group are prepared by two-step emulsion polymerisation. In the first step, the seeds are synthesised by batch emulsion polymerisation of styrene in the second step, two different amino-functionalised monomers... 

Cationic latex particles with surface amino groups were prepared by a multi-step batch emulsion polymerisation. Monodisperse cationic latex particles to be used as the seed were synthesised first. Then the amino-functionalised monomer, aminoethylmethacrylate hydrochloride, was used to synthesise the final functionalised latex particles. Three different azo initiators were used 2,2 -azobisisobutyramidine dihydrochloride, 2,2 -azobisdimethyleneisobutyramidine dihydrochloride, and 2,2 -azobisisobutyronitrile. Hexadecyltrimethylammonium bromide was used as the emulsifier. The latices were characterised by photon correlation spectroscopy to study the mean particle diameters, transmission electron microscopy to deteimine the particle size distributions, and hence the number- and weight-average diameters and the polydispersity index. The conversion was determined gravimetrically, the surface density of the amino groups was detemiined by conductimetric titrations, and the... 

A limited number of studies focussed on the development of NHC-Pd catalysts for polymerisation reactions. The a-ketone arylation reactions, described in Section 9.2.8, can be applied to the polycondensation of haloarylketones. Thus, Matsubara reported the polymerisation of bromo- or chloro-propiophenone catalysed by mixtures of [Pd(OAc)2] and IPr HCl or IMes HCl (3 mol% [Pd]). The former system was more active and the use of excess imidazolium salts resulted in decreased activity, due to the formation of bis-NHC Pd species. Chung reported the application of Nolan-type Pd-allyl catalysts (see Figure 9.8) to the polymerisation of ester-functionalised norbornene monomers. " These substrates are typically more difficult to polymerize than non-functionalised monomers, and such catalysts efficiently catalysed the polymerisation of simple... 

We may draw a distinction in basic mechanism of formation of polymers and this is indicated schematically in Figure 5. For functionalised monomers e.g. an alkene it is possible under certain conditions to produce linear polymers. These arise from conventional cationic or radical addition mechanism the plasma then acting as a source of reactive intermediates to initiate the 2 plasma. This is termed plasma induced polymerizations (PIP). 

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