Anionic polymerization hydroxylation

Other Organolithium Compounds. Organoddithium compounds have utiHty in anionic polymerization of butadiene and styrene. The lithium chain ends can then be converted to useflil functional groups, eg, carboxyl, hydroxyl, etc (139). Lewis bases are requHed for solubdity in hydrocarbon solvents. 

PS-b-PEO) , n = 3, 4 star-block copolymers were synthesized by ATRP and anionic polymerization techniques [149]. Three- or four-arm PS stars were prepared using tri- or tetrafunctional benzylbromide initiators in the presence of CuBr/bipy. The polymerization was conducted in bulk at 110 °C. The end bromine groups were reacted with ethanolamine in order to generate the PS stars with hydroxyl end groups. These functions were then activated by DPMK to promote the polymerization of ethylene oxide and afford the desired well-defined products (Scheme 73). 

Double hydrophilic star-block (PEO-fo-PAA)3 copolymers were prepared by a combination of anionic and ATRP of EO and fBuA [150]. Three-arm PEO stars, with terminal - OH groups were prepared by anionic polymerization, using l,l,l-tris(hydroxymethyl)ethane, activated with DPMK as a trifunctional initiator. The hydroxyl functions were subsequently transformed to three bromo-ester groups, which were utilized to initiate the polymerization of f-butyl acrylate by ATRP in the presence of CuBr/PMDETA. Subsequent hydrolysis of the f-butyl groups yielded the desired products (Scheme 74). 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

Depending on polymerization conditions, PEG termini may consist of hydroxyl groups or may be selectively functionalized. Commercially available PEG is produced through anionic polymerization of ethylene oxide to yield a polyether struc-... 

Block copolymers of (R,S)-(3-butyrolactone and eCL have been synthesized by combining the anionic ROP of the first monomer with the coordinative ROP of the second one (Scheme 15) [71]. The first step consisted of the synthesis of hydroxy-terminated atactic P(3BL by anionic polymerization initiated by the alkali-metal salt of a hydroxycarboxylic acid complexed with a crown ether. The hydroxyl end group of P(3BL could then be reacted with AlEt3 to form a macroinitiator for the eCL ROP. 

The anionic polymerization of 2-furyl oxirane 4a (17) proceeds smoothly and can be made to yield oligomers bearing a hydroxyl group at each end ... 

A dual-function alkoxyamine with an appropriate functional group, such as the hydroxyl-containing alkoxyamine LX, can initiate anionic polymerization (in the presence of... 

Graft copolymer, polyclhylene-gra/f-poly(propylcnc oxide) (PE-g-PPG), has been synthesized by ring opening anionic polymerization of propylene oxide with a phosphazene catalyst and hydroxylated polyethylene (Mn = 12400, [OH] = 5 units/chain). Polymerization of propylene oxide was carried out in tetraline at 120 °C for 20 hours. The 13C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization (Fig. 6). 

Polyclhylcnc-gra/f-polycaprolaclonc (PE-g-PCL) was synthesized by ring opening anionic polymerization of e-CL with a triethylalminum catalyst and hydroxylated PE. Polymerization of e-CL was performed in toluene for 24 hours. The obtained PE-g-PCL, in which 36-80 mol % of the hydroxyl groups worked as initiators for e-CL polymerization, possessed 29 units of e-CL in polymer hybrids (Fig. 7). 

The first block (polybutadiene or polystyrene) is prepared by anionic polymerization, under high vacuum, in THF dilute solution (less than 5%), at low temperature (—70 °C) with cumylpotassium as initiator. Then, the living polymer is transformated into a hydroxylated polymer (PV—OH) by addition of ethylene oxide under vacuum, or into a carboxylated polymer (PV-COOH) by addition of carbon dioxide under vacuum. 

Anionic polymerization of EtG leads to a new synthetic biodegradable polymer, namely poly(ethyl glyoxylate). Because of a low ceiling temperature and transfer reactions, PEtG has hydroxyl ends that can be end-capped with phenyl isocyanate. 

Living anionic polymerization of methacrylates and acrylates can be used to prepare macromonomers, which can thereafter be polymerized by any technique known in the state of the art. For instance, Flatada and coworkers reacted anionic ft)-hydroxyl-PMMA (55), which was then polymerized by radical polymerization into the corresponding combshaped copolymer (81) with 2,2 -azobis(isobutyronitrile) (AIBN) as initiator (equation 64). ... 

B-90 and B-91, respectively.390 Another route coupled with cationic ring-opening polymerizations is accomplished for polymer B-92 with the use of a hydroxyl-functionalized initiator with a C—Br terminal, where the OH group initiates the cationic polymerizations of 1,3-dioxepane in the presence of triflic acid.329 Polyethylene oxide)-based block copolymers B-93 are obtained by living anionic polymerization of ethylene oxide and the subsequent transformation of the hydroxyl terminal into a reactive C—Br terminal with 2-bromopropionyl bromide, followed by the copper-catalyzed radical polymerization of styrene.391... 

A combination of other polymerization pathways also results in some hyperbranched structures. Multifunctional hydroxyl groups in polyglycerol with hyperbranched structure, prepared by anionic polymerization of glycidol, were esterified with 2-bro-moisobutyroyl bromide and then employed as a hyperbranched multifunctional macroinitiator for the copper-catalyzed radical polymerization of MA to give products with 45—55 poly(MA) arms.449... 

---