Acrylic acid polymerization block copolymers

Block copolymers between alkyl acrylates such as B-4,358 B-5,202,203 and B-6,203 on the other hand, have been synthesized by the macroinitiator methods mostly with copper catalysts. Star block copolymers with a soft poly(MA) core and a hard poly(isobomyl acrylate) shell were synthesized by using multifunctional initiators.358 Poly(tBA) segments in B-5 and B-6 can be converted into hydrophilic poly(acrylic acid).203 Block copolymers between />methylstyrene and styrene (B-7) were also prepared by the rhenium-catalyzed living radical polymerization in conjunction with an alkyl iodide initiator.169... 

Another template-free method for the formation of self-assembled tubular structures has been shown by Jiang and co-workers. They used polymeric Janus particles prepared from mixed-shell micelles (MSMs) that self-assembled into tubular superstructures and nanosheets. The micelles were prepared by non-covalent cross-linking of poly(acrylic acid) (PAA) blocks by addition of 1,2-propanediamine (PDA) in DMF (A on Figure 5.45). The two block copolymers were composed of hydrophilic poly(ethylene... 

Rager, T., Meyer, W.H. and Wegner, G. (1999) Micelle formation of PAA-PMMA block copolymers in mixtures of water with organic solvents. Macromol. Chem. Phys., 200,1672-1680. LarueUe, G., Pran9ois, J. and Billon, L. (2004) Self-assembly in water of poly(acrylic acid) based diblock copolymers synthesized by nitroxide-mediated polymerization. Macromol. Rapid Commun., 25,1839-1844. 

The synthesis of cylindrical polymer brushes with amphiphilic poly(acrylic acid)-block-poly(n-butyl acrylate) (PAA-b-PnBA) diblock copolymer side chains is shown in Fig. 13.14. The procedure includes several steps (i) synthesis of a well-defined macroinitiator, PBIEM, by esterification of poly(2-hydroxyethyl methacrylate) (PHEMA), which was synthesized via ATRP of 2-hydroxyethyl methacrylate (HEMA) or anionic polymerization of silyl-protected HEMA (ii) ATRP of t-butyl acrylate (tB A) initiated by the pendant a-bromoester groups of PBIEM, yielding cylindrical brushes with PtBA homopolymer side chains (iii) sequential ATRP of n-butyl acrylate (nBA) forming the cylindrical bmshes with diblock copolymer [poly(t-butyl acrylate)-block-poly(n-butyl acrylate) (PtBA-b-PnBA)] side chains and (iv) hydrolysis of the PtBA block to produce the hydrophilic poly(acrylic acid) (PAA) block forming the core of an amphiphilic core-shell cylinder brash [106]. By using this technique, other well-defined core-shell cylindrical polymer brashes with polystyrene (PS), PS-b-PAA or PAA-b-PS, as side chains have been successfully synthesized. 

RAFT polymerization has been used to prepare poly(ethylene oxide)-/ /wA-PS from commercially available hydroxy end-functional polyethylene oxide).4 5 449 Other block copolymers that have been prepared using similar strategies include poly(ethylene-co-butylene)-6/oci-poly(S-eo-MAH), jl poly(ethylene oxide)-block-poly(MMA),440 polyethylene oxide)-Moe -poly(N-vinyl formamide),651 poly(ethylene oxide)-Wot A-poly(NlPAM),651 polyfethylene ox de)-b ock-polyfl,1,2,2-tetrahydroperfluorodecyl acrylate),653 poly(lactic acid)-block-poly(MMA)440 and poly( actic acid)-6focA-poly(NIPAM),4 8-<>54... 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Monofunctional and difunctional xanthates, shown in Scheme 30, were employed as chain transfer agents in the synthesis of block and triblock copolymers of acrylic acid, AA and acrylamide, AAm PAA-fr-PAAm, PAAm-fr-PAA-fo-PAAm and P(AA-sfaf-AAm)-fr-PAAm [81]. The polymerizations were conducted in aqueous solutions at 70 °C with 4,4 -azobis(4-cyanopentanoic acid) as the initiator. The yields were almost quantitative,... 

Carboxylated polymers can be prepared by mechanical treatment of frozen polymer solutions in acrylic acid (Heinicke 1984). The reaction mechanism is based on the initiation of polymerization of the frozen monomer by free macroradicals formed during mechanolysis of the starting polymer. Depending on the type of polymer, mixed, grafted, and block polymers with a linear or spatial structure are obtained. What is important is that the solid-phase reaction runs with a relatively high rate. For instance, in the polyamide reactive system with acrylic acid, the tribochemical reaction leading to the copolymer is completed after a treatment time of 60 s. As a rule, the mechanical activation of polymers is mainly carried out in a dry state, because the structural imperfections appear most likely here. 

Photolysis of this polymer gives radicals on which side chains can be formed, giving graft polymerization 122, 123, 153). Similarly the polymerization of styrene (152) or vinyl acetate (157) in the presence of bromotrichloromethane gives telomers carrying terminal bromine atoms and trichloromethyl groups. By ultraviolet irradiation (3500 A) in the presence of methyl methacrylate the carbon-bromine links are broken and block copolymers are formed. The telomerization of acrylonitrile and acrylic acid with bromoform is based on the same technique the end groups of both polyacrylonitrile and polyacrylic acid were photolyzed in the presence of acrylamide and afforded polyacrylamide blocks linked to polyacrylonitrile or polyacrylic acid blocks (164, 165). 

Polymeric steric stabilizer such as poly(vinylpyrrolidone) (PVPo),poly(acrylic acid), poly(hydroxypropyl)cellulose, etc., are used to prepare monodisperse polymer in dispersion polymerization of monomers such as alkyl acrylates and methacrylates, and styrene in polar media. AB and ABA block copolymers are a second type of steric stabilizer which can be used in dispersion polymerization. For example, the poly(styrene-h-ethylene oxide) was recently used by Winnik et al. [6] in the dispersion polymerization of styrene in methanol. 

In the case of inverse systems, hydrophilic monomers such as hydroxyethyl acrylate, acrylamide, and acrylic acid were miniemulsified in non-polar media, e.g., cyclohexane or hexadecane [45,46]. Rather small and narrow distributed latexes in a size range between 50 nmsynthesized with nonionic amphiphilic block copolymers. Depending on the system, the surfactant loads can be as low as 1.5 wt% per monomer, which is very low for an inverse heterophase polymerization reaction and clearly underlines the advantages of the miniemulsion technique. 

With the purpose of increasing the range of available block copolymers, comonomers other than methacrylates and acrylates can also be involved in sequential polymerization, provided that they are susceptible to anionic polymerization. Dienes, styrene derivatives, vinylpyridines , oxiranes and cyclosiloxanes are examples of such comonomers. The order of the sequential addition is, however, of critical importance for the synthesis to be successful. Indeed, the pX a of the conjugated acid of the living chain-end of the first block must be at least equal to or even larger than that of the second monomer. Translated to a nucleophilicity scale, this pK effect results in the following order of reactivity dienes styrenes > vinylpyridines > methacrylates and acrylates > oxiranes > siloxanes. 

Mesophases prepared by dissolution of the copolymer in a preferential solvent for the poly(vinylpyridine) block (acrylic acid, nitromethane, dfoxane, octanol, methylethyl ketone, ethyl acetate, vinyl acetate, styrene and methyl methaaylate) and dry copolymers obtained by slow evaporation of the solvent from the mesophases have been studied by low-angle X-r diffraction electron microscopy Copolymers of isoprene and vinylpyridine exhibit cylindrical hexagonal or lamellar structures dependii upon their comi siton.The influence of the nature, concentration, and polymerization of the solvent, molecular weight and composition of the copolymer, microstructure of the polyisoprene block, and position of the nitrogen atom in the vinylpyridine block on the values of the geometrical parameters of the periodic structures have been establidied ... 

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