Poly(2-oxazoline)-Containing Triblock Copolymers: Synthesis and Applications

Abstract

This review focuses on poly(2-oxazoline) containing triblock copolymers and their applications. A detailed overview of the synthetic techniques is provided. Triblock copolymers solely based on poly(2-oxazoline)s can be synthesized by sequential monomer addition utilizing mono- as well as bifunctional initiators for the cationic ring-opening polymerization of 2-oxazolines. Crossover and coupling techniques enable access to triblock copolymers comprising, e.g., polyesters, poly(dimethylsiloxane)s, or polyacrylates in combination with poly(2-oxazoline) based segments. Besides systematic studies to develop structure property relationships, these polymers have been applied, e.g., in drug delivery, as (functionalized) vesicles, in segmented networks or as nanoreactors.

Keywords:

• Cationic ring-opening polymerization
• poly(2-oxazoline)
• triblock copolymer
• telechelics
• bifunctional initiator
• polymerization mechanism switch

Abbreviations
ABuOx	=	2-(4-amino)butyl-2-oxazoline;
CH3CN	=	acetonitrile;
AFM	=	atomic force microscopy;
BBMBP	=	4,4′-bis(bromomethyl)biphenyl;
bpy(CH2Cl)2	=	5,5′-bis(chloromethyl)-2,2′-bipyridine;
BuOx	=	2-n-butyl-2-oxazoline;
ButenOx	=	2-(3-butenyl)-1,3-oxazoline;
CEtOx	=	2-carboxyethyl-2-oxazoline;
CinFOx	=	N-(10-(4,5-dihydrooxazol-2-yl)decyl)cinnamamide;
CMC	=	critical micelle concentration;
CPOx	=	2-cyclopropyl-2-oxazoline;
CROP	=	cationic ring-opening polymerization;
CTA	=	chain transfer agent;
CuACC	=	copper-catalyzed azide alkyne cycloaddition;
DBX	=	α,α′-dibromo-p-xylene;
DiFPhOx	=	2-(2,6-difluorophenyl)-2-oxazoline;
DiIP	=	1,3-diiodopropane;
DLS	=	dynamic light scattering;
DMSO	=	dimethyl sulfoxide;
DMTA	=	dynamic thermal mechanical analysis;
DP	=	degree of polymerization;
DSC	=	differential scanning calometry;
EPOx	=	2-(1-ethylpentyl)-2-oxazoline;
Et(OTs)2	=	ethylene di(p-toluenesulfonate);
EtOx	=	2-ethyl-2-oxazoline;
HeptOx	=	2-heptyl-2-oxazoline;
iBuOx	=	2-isobutyl-2-oxazoline;
iPentOx	=	2-isopentyl-2-oxazoline;
iPrOx	=	2-isopropyl-2-oxazoline;
LCST	=	lower critical solution temperature;
MALDI-ToF MS	=	matrix assisted laser absorption–desorption ionization – time of flight mass spectrometry;
MeONs	=	methyl 4-nitrobenzenesulfonate;
MeOTf	=	methyl triflourmethylsulfonate;
MeOTs	=	methyl p-toluenesulfonate;
MeOx	=	2-methyl-2-oxazoline;
MPEG-OTs	=	poly(ethylene glycol) methyl ether p-toluenesulfonate;
MTT	=	3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide;
NMP	=	nitroxide mediated polymerization;
NonOx	=	2-nonyl-2-oxazoline;
OctOx	=	2-octyl-2-oxazoline;
Ox	=	2-oxazoline;
PBD	=	polybutadiene;
PCL	=	polycaprolactone;
PDMS	=	polydimethylsiloxane;
PEG	=	poly(ethylene glycol);
PEI	=	poly(ethylene imine);
PentOx	=	2-n-pentyl-2-oxazoline;
PEVE	=	poly(ethyl vinyl ether);
PFPhOx	=	(2,3,4,5,6-pentafluorophenyl)-2-oxazoline;
PhOx	=	2-phenyl-2-oxazoline;
PLA	=	poly(lactic acid);
PMHS	=	poly(methylhydrosiloxane);
POx	=	poly(2-oxazoline)s;
PPO	=	poly(propylene oxide);
Propargyl-OTs	=	propargyl p-toluenesulfonate;
PrOx	=	2-n-propyl-2-oxazoline;
PS	=	polystyrene;
PTHF	=	polytetrahydrofuran;
RAFT	=	reversible addition-fragmentation chain transfer;
ROP	=	ring-opening polymerization;
SAXS	=	small-angle X-ray scattering;
SEC	=	size exclusion chromatography;
SANS	=	small angle neutron scattering;
secBuOx	=	2-sec-butyl-2-oxazoline;
Sn(oct)2	=	tin(II) octoate;
TDBB	=	trans-1,4-dibromo-2-butene;
TEM	=	transmission electron microscopy;
TetFPhOx	=	2-(2,3,4,6-tetrafluorophenyl)-2-oxazoline;
TREN	=	N,N-bis(2-aminoethyl)ethylenediamine;
TriFPhOx	=	2-(2,4,6-trifluorophenyl)-2-oxazoline;
UnOx	=	2-undecyl-2-oxazoline;
UV	=	ultraviolet;
WAXS	=	wide-angle X-ray scattering

Additional information

Funding

The work was supported by the DFG-funded collaborative Research Centre PolyTarget (SFB 1278, projects A01 and Z01).