Polyethylene glycol triblock copolymers

A series of poly(ester-urethane) urea triblock copolymers have been synthesized and characterized by Wagner et al/ using PCL, polyethylene glycol, and 1,4 diisocyanatobutane with either lysine ethyl ester or putrescine, as the chain extender. These materials have shown the elongation at break from 325% to 560% and tensile strengths from 8 to 20 MPa. Degradation products of this kind of materials did not show any toxicity on cells. 

The anionic method of polymerization is most useful for the synthesis of low molecular weight hydroxy-terminated oligomers and polymers that are to be further processed. For example, the treatment of hydroxy-terminated oligomers with isocyanates has been used to obtain polyester-urethanes (9,20), while triblock copolymers (PCL-PEG-PCL) are prepared by initiating the polymerization of e-caprolactone with the disodium alcoholate from polyethylene glycol (26). 

If mono-hydroxyl functionalized polyethylene glycol), HO-PEG, is added to Ca(NTMS2)2.THF2, then addition of LA affords the diblock PEG-b-PLA (Mn= 15,500, Mn calc = 15,500, Mw/Mn = 1.03).832 Using a similar strategy the reaction of CaFI2 with telechelic diol HO-(PEG)-OH, followed by polymerization of L-LA results in a triblock structure, PLA-b-PEG-b-PLA of narrow polydispersity (1.02-1.08).835 836 Triblock copolymers of morpholine-2,5-diones with PEO have also been prepared in this manner.837... 

Yui and coworkers prepared CD-based polyrotaxane of Type 5 by capping the cyclic on a triblock copolymer of polyethylene glycol) and polypropylene glycol) using a blocking group [92]. When the peptide linkage was between PEO and the BG, the thermal stability of the polyrotaxane was related to disassociation... 

Amphiphilic triblock copolymers were prepared from polyethylene glycol) (PEG) [35], Starting from PEG segments of different lengths (Mw = 200,400, MO, 1000 and 1500) and with different end-groups (e,g, hydroxy, acetoxy, benzoyl, oleoyl, phenylurethane), telechelic macroazoinitiators are first prepared. By polymerization of styrene, a wide range of original copolymers are produced ... 

Polyethylene glycol) (PEG)-based di- and triblock copolymers were prepared in a similar approach from the corresponding hydroxyl-functionalized PEG macroinitiators. Kaplan conducted a detailed mechanistic and kinetic study of the interplay between monomer conversion, chain initiation and chain propagation... 

Polyethylene glycol (PEG) is another well-known molecule used to reduce protein adsorption and/or platelet adhesion. Surface enrichment of a triblock oligomeric PEG containing additive from a polyurethane matrix was reported [54,55]. The authors used PEG as the active groups to suppress protein and platelet adhesion. The authors first synthesized a methylene diphenyl diisocyanate (MDI)-poly (tetramethylene oxide) (PTMO) 1000 prepolymer with a MW of approximately 4750 (PU4750), and then this prepolymer was terminally functionalized with mono amino-polyethylene oxide (PEG) with different MW (PEO550, 2000, or 5000, Table 2.3). This triblock copolymer was mixed with a polyurethane (MDI/ PTMO 1000/ethylene diamine (ED)) at different ratios in dimethylformamide (DMF) and cast into polymer films. The surface compositions of these films were evaluated by XPS. 

If the initiator itself is polymeric in nature, for example, polyethylene glycol (PEG), lactide can polymerize from the hydroxyl end group(s) of PEG resulting in PEG-PLLA diblock or triblock copolymers. 

Apart from polyethylene glycols, Sadeghi et al. [185, 235, 236] used polyvinyl pyrrolidone (PVP) with trisodium and tripotassium citrates in establishing the aqueous two-phase systems. The binodal curves and tie-lines in these systems were determined in the 25-55 °C temperature range. Polyethylene oxide (PEG) and polypropylene oxide (PPG) were also utilized to form the aqueous two-phase systems with trisodium citrate. For example, daRocha Patricio etal. [237] investigated PEG 1500 systems at 10, 25 and 40 °C. Two-phase systems consisting water, triblock copolymers formed from ethylene oxide and propylene oxide units and trisodium citrate were smdied at 15, 35 and 45 °C by drtuoso et al. [238]. 

Hyun et al have decribed synthesis of PTMC-PEG-PTMC triblock and methyl polyethylene glycol (MEPEG)-PTMC diblock copolymers according to the cationic polymerization mechanism using PEG or monomethoxy-PEG and HCl OEt2 as an initiation system for TMC polymerization. 

Other recent applications of ToF-SIMS without XPS include the examination of PS [6, 17-19], polyethylene (PE) [20], carbon fibre reinforced epoxy resins [21], polyalkyl methacrylates [22], alkylketene dimers [23], perfluorinated polymers [24], perflnorinated ethers [25], polyethylene glycol (PEG) oligomers [15, 25-29], rubber [30], ethylene-tetrafluoroethylene copolymer [30], Nylon-6 [31], PC [32,33], PDMS [34], polypyrrole coated PS [35], poly-p-phenylene vinylene [36], butyl rubber [37], poly(4-vinyl phenol)/poly(4-vinyl pyridine blends) [38], polypyrrole-silica gel composites [39], y-glycidoxypropyl trimethoxy silane [40], triblock copolymer poly(ethylene glycol)- 3 poly(phenylene ethylene)- 3 poly(ethylene glycol) [41], ethylene-terephthalate-hydroxybenzoate copolymer [42], PS-polyvinyl methyl ether, polycarbonate - PS blends [43] and PDMS-urethane [44],... 

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