Propose one-stage methods for the synthesis of styrene-maleic anhydride diblock copolymers using the RAFT technique. Draw appropriate schemes and formulas



One-stage synthesis of diblock copolymers
Monofunctional OPC-agent - chain growth at one end

Stirol> maleic anhydride

Propose two-stage methods for the synthesis of triblock copolymers using the RAFT technique. Draw appropriate schemes and formulas.

ABC triblock copolymers incorporating the active monomer N-acryloxysuccinimide and the formation of shell cross-linked (SCL) micelles

When solutions of polymer micelles are diluted below the critical micelle concentration (CMC), dissociation to unimers occurs. Therefore, under conditions of high dilution (e.g., in vivo), polymeric micelle stability is compromised, and the potential for controlled-delivery applications is reduced. To circumvent this limitation, several groups have explored stabilization of the micelle corona through chemical or physical cross-linking. These stabilized micelles, commonly referred to as shell cross-linked (SCL) micelles, were first reported by Wooley and coworkers60 in 1996 and are the subject of a recent review by Armes et al.61SCL micelles have potential applications in drug delivery, emulsification, sequestration of metabolites, and entrapment of environmental pollutants.62–68 Recently, we44 synthesized ABC triblock copolymers of poly(ethylene oxide) (PEO)-b-P((DMA-stat-N-acryloxysuccinimide (NAS))-b-NIPAM) (Scheme 4) and demonstrated the facile formation of SCL micelles. One hydrophilic segment of the ABC triblock copolymer was comprised of PEO, selected on the basis of demonstrated biocompatibility and dual solubility in both aqueous and organic media. Incorporation of PEO segments into block copolymersprepared by RAFT is generally accomplished by first preparing a macroCTA from ω-hydroxy PEO.69,70Polymerization in the presence of such a RAFT agent allows in situblock copolymer formation. A procedure similar to that reported by Perrier and coworkers was employed to prepare the PEO macroCTA necessary for synthesis of PEO-b-P((DMA-stat-NAS)-b-NIPAM) (Scheme 4).71 NAS units in the resulting block copolymer demonstrated minimal susceptibility to hydrolysis and served as internal crosslinking sites for reaction with difunctional primary amines.72 The thermoresponsive block of the copolymer was prepared by RAFT polymerization of NIPAM.

A symmetric, acyclic olefin possessing trithiocarbonate moieties, available in two synthetic steps from commercially available starting materials, is demonstrated to act as a chain transfer agent (CTA) in ring opening metathesis polymerizations (ROMP). The synthetic efficiency of the ruthenium-catalyzed ROMP of 1,5-cyclooctadiene in the presence of this new CTA is investigated as a means of producing telechelic polybutadienes bearing trithiocarbonate endgroups.

23.  Synthesize temperature- and redox-responsive multi-block copolymers of poly(N-isopropylacrlamide) (PNIPAAM) and poly(dimethylaminoethylmethacrylate) (PDMAEMA) by RAFT polymerization. Draw appropriate schemes and formulas.

 

 

 For the production of multiblock copolymers, this obviously is not the preferred route.

The well-defined block copolymer of poly[ethylene oxide)-b-poly(N-isopropylacrlamide) (PEO-b-PNIPAM) was synthesized by Liang and coworkers via RAFT polymerisation using monofunctional PEO macro-RAFT agen).

24 Propose method for the synthesis brush type graft copolymers via ATRP approach.

Schematic presentation of the immobilization of surface initiator and polymerization of vinyl monomers via ATRP

Scheme 33.

The synthesis of PHA-g-PMMA, PHA-g-PS, PHA-g-PBMA brush type graft copolymers via ATRP

Recently many studies on the synthesis of graft copolymers via ATRP in the literature have been also reported. Some of them are listed in

In some cases, different controlled polymerization systems are combined to produce block and graft copolymers

Lu et al reported the synthesis of block and graft copolymers of β-pinene and styrene by combination of living cationic polymerization and atom transfer radical polymerization methods (Scheme 34) [105].

Block copolymer synthesis via a combination of ATRP and RAFT using click chemistry was reported by Webster and co-workers (Scheme 35) [106].

 

1st Segment 2nd Segment Ref.
Chitosan Cellulose Cellulose Si/PGMA PBIEM-I MWNTs PVDF Si Si Si P(OEGMA) PMMA PS PS PMAIpGlc PMAIpGlc PMAGlc PMMA PHEMA PDMAEMA [96] [97] [97] [98] [99] [100] [101] [102] [103]

 

25. Propose method for the synthesis of polystyrene grafted chitosan via NMP using chitosan-TEMPO macroinitiator.

Graft copolymerization via NMP

Hua et al. prepared polystyrene grafted chitosan (Scheme 25) via NMP using chitosan-TEMPO macroinitiator.

Figure 8.

Schematic presentation of Grafting-through

Scheme 25.

Synthesis of Chitosan-g-PSt by NMP

26. Propose method for the synthesis of styrene-acrylic acid amphiphilic diblock-gradient copolymer via nitroxide-mediated polymerization.

27. Propose method for the synthesis of styrene-acrylic acid amphiphilic triblock-gradient copolymer via nitroxide-mediated polymerization

Polymers which are composed of two different monomers are usually referred to as copolymers. In a linear block copolymer, the monomeric residues are arranged in such a way that one block consists of monomeric residue A and another block of monomeric residue B. These methods utilized so-called iniferters, i.e. compounds which could serve as INItiators, transFER agents and TERminating agents. However, while useful, these techniques did not offer the desired level of control over macromolecular structure, due to poor molecular weight control, high polydispersities, and low blocking efficiency. d. These techniques are referred to as controlled radical polymerizations, such as Nitroxide-Mediated Polymerization (NMP), Atom Transfer Radical Polymerization (ATRP) and Reversible Addition-Fragmentation chain Transfer (RAFT) and are based on two principles: reversible termination and reversible transfer. Two basic strategies have been applied to initiate NMP. The first method involves use of a conventional initiator (e.g. AIBN, BPO) in the presence of a nitroxide and this system is called as “bimolecular NMP”. The second method is called as “unimolecular NMP” (Scheme 2) and it is possible when the initiator is a low molecular weight alkoxyamine.

Controlled radical polymerization in the presence of nitroxides - an effective way of obtaining a new type amphiphilic block-gradient copolymers.

 


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