Jørgen Kops

Synthesis of photoreactive α‐4‐azidobenzoyl‐ω‐methoxy‐poly(ethylene glycol)s and their end‐on photo‐grafting onto polysulfone ultrafiltration membranes

Covalent end-on grafting of poly(ethylene glycol) (PEG) onto a polysulfone (PSf) surface using α-4-azidobenzoyl-ω-methoxy-PEG (ABMPEG) is described. Photoreactive ABMPEG was synthesized by reacting monomethoxy-PEG (MPEG) with 4-azidobenzoyl chloride, yielding complete substitution of the hydroxyl groups. After adsorption from aqueous solutions, ABMPEG was photo-grafted under wet conditions onto PSf ultrafiltration (UF) membranes. Contact angle (CA) measurements showed the increased hydrophilicity of modified membranes and the irreversibility of the modification. Bovine serum albumin (BSA) adsorption decreased by 70% and the permeability decay after protein adsorption became less severe for the modified membranes compared to unmodified reference membranes.

Synthesis by ATRP of poly(ethylene‐co‐butylene)‐block‐polystyrene, poly(ethylene‐co‐butylene)‐block‐poly(4‐acetoxystyrene) and its hydrolysis product poly(ethylene‐co‐butylene)‐block‐poly(hydroxystyrene)

Diblock copolymers of poly(ethylene-co-butylene) and polystyrene or poly(4-acetoxystyrene) are synthesized by atom transfer radical polymerization (ATRP) using a 2-bromopropionic ester macroinitiator prepared from commercial monohydroxyl functional narrow dispersity hydrogenated polybutadiene (Kraton Liquid Polymer, L-1203). ATRP carried out in bulk and in xylene solution with cuprous bromide and two different complexing agents 2,2′-bipyridine (bipy) and 1,1,4,7,10,10-hexamethyltriethylenetetraamine (HMTETA) yielded well-defined diblock copolymers with polydispersities around 1,3. The diblock copolymer with poly(4-acetoxystyrene) was hydrolyzed to the corresponding poly(4-hydroxystyrene) sequence.

Synthesis of isobutenyl-telechelic polyisobutylene by functionalization with isobutenyltrimethylsilane

Abstract Isobutenyl-telechelic polyisobutylenes (PIBs) were synthesized by reacting tert-chlorine-telechelic and living PIBs with isobutenyltrimethylsilane (IBTMS) in the presence of TiCl4 in CH2Cl2/hexane (40/60 v/v) solvent mixtures at −78°C. In order to obtain PIB oligomers, living polymerization of isobutylene was induced by the di-(2-hydroxy-2-propyl)-5-tert-butylbenzene (tBuDiCumOH)/BCl3 combination in CH2Cl2 followed by addition of required amounts of hexane and TiCl4 to avoid polymer precipitation and permanent termination. Although quantitative end-quenching of living PIB was achieved with IBTMS, chain coupling between the living PIB chains and isobutenyl-ended polymers also occurred. This side reaction was avoided by isobutenylation of tert-chlorine-telechelic PIB with IBTMS in the presence of TiCl4. The resulting isobutenyl-telechelic PIB contains exclusively exoCH2C(CH3)CH2 endgroups, and is free from CHC(CH3)2 endo olefins usually obtained in small quantities (∼3–8% of total double bonds) as a side product of other methods used in the past.

Synthesis by ATRP of triblock copolymers with densely grafted styrenic end blocks from a polyisobutylene macroinitiator

polyisobutylene macroinitiator DTU Orbit (18/07/2019) Synthesis by ATRP of triblock copolymers with densely grafted styrenic end blocks from a polyisobutylene macroinitiator A macroinitiator was prepared from a triblock copolymer of polyisobutylene (PIB) with end blocks of poly(p-methylstyrene) (P(p-MeS)) by bromination to obtain initiating bromomethyl groups for atom transfer radical polymerization (ATRP). Controlled polymerization of styrene and p-acetoxystyrene yields new triblock copolymer structures with densely grafted end blocks. Simultaneously, however, thermally initiated polymerizations can be observed by size exclusion chromatography (SEC) which were also controlled yielding low molecular weight polymers with narrow distributions. A tendency to crosslinking can be suppressed by selection of the polymerization conditions.

Preparation of polystyrene-poly(ethylene glycol) diblock copolymer by ‘living’ free radical polymerisation

Abstract Amphiphilic diblock copolymer containing segments of polystyrene and monomethoxypoly(ethylene glycol) (PS-b-PEG) was synthesised by a novel method. Initially, the adduct (BZ-TEMPO) obtained by reacting benzoyl peroxide, styrene, and 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) was isolated, characterised and hydrolysed. Conditions for the synthesis and hydrolysis of BZ-TEMPO were investigated and the hydrolysed product (HO-TEMPO) containing a primary hydroxyl group has been isolated in improved yield. The hydroxyl group of HO-TEMPO was coupled with tosylated PEG to yield the macroinitiator PEG terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer PS-b-PEG by ‘living’ free radical polymerisation of styrene. The product was purified and identified by 1H n.m.r. and GPC. However, large amounts of homopolystyrene was also formed by simultaneous thermal initiation and polymerisation.

Living carbocationic polymerization of isobutylene and synthesis of ABA block copolymers by conventional laboratory techniques

SummaryLiving polymerization of isobutylene (IB) and subsequent controlled synthesis of ABA block copolymers, such as poly(styrene-b-isobutylene-b-styrene) (PSt-PIB-PSt) and poly(p-methylstyrene-b-isobutylene-b-p-methylstyrene) (PpMeSt-PIB-PpMeSt), have been carried out by a simple and inexpensive conventional laboratory technique. The homo- and block copolymers obtained by using this technique have exhibited excellent molecular weight control and low polydispersity indexes. The living nature of IB polymerization has been demonstrated by the incremental monomer addition (IMA) method with the dicumyl methyl ether (DiCumOMe)/TiCl4 initiating system in the presence of 2,5-di-tert-butylpyridine (DtBP) proton trap. PSt-PIB-PSt and PpMeSt-PIB-PpMeSt block copolymers have been synthesized by sequential monomer addition: first living difunctional polyisobutylene (PIB) midsegment was prepared by difunctional initiator, then the second monomer was added to the charge. High blocking efficiencies and desired block copolymer structures have been obtained.

Synthesis of tri-block copolymer based on polyisobutylene and poly(ethylene glycol)

SummaryA block copolymer having polyisobutylene (PIB) as hydrophobic segment and poly(ethylene glycol) (PEG) as hydrophilic segments has been synthesized by a two-step process. Polyisobutylene was functionalized with phenol at both ends using BF3· OEt2 as catalyst, and then coupled with tosylated monomethoxy PEG. The reaction conditions were established by model studies. The characterization of the reaction product by NMR and PGC verified the formation of block copolymer by the coupling reaction.

Hydrolysis of 4-acetoxystyrene polymers prepared by atom transfer radical polymerization

Hydrolysis of 4-acetoxystyrene polymers prepared by atom transfer radical polymerization was carried out under various reaction conditions. It was found that hydrazinolysis of 4-acetoxystyrene homopolymers, random and block copolymers with styrene in 1,4-dioxane, afforded the corresponding narrow dispersed materials with phenolic groups which were substantially free from crosslinkages. Gel permeation chromatographic (GPC) analysis of these polymers revealed different extents of molecular weight distribution (MWD) broadening for the hydrolysis products for the different structures. On the other hand, by NaOH catalyzed deprotection, the 4-acetoxystyrene polymers including triblock copolymer poly(4-acetoxystyrene-b-isobutylene-b-4-ace-toxystyrene) suffered from some degrees of coupling or even gelation, except for poly-(styrene-b-4-acetoxystyrene-b-styrene) which also by this method could be conveniently converted to its phenolic product.

Novel polymeric surfactants: Synthesis of semi-branched, non-ionic triblock copolymers using ATRP

This article reports the synthesis of novel amphiphilc triblock copolymers with a semi-branched PLURONIC®R structure by atom transfer radical polymerization (ATRP) in aqueous media. Poly(ethylene oxide)s (PEOs) with molecular weights 10 000 and 16 000 were end-functionalized and used as bifunctional macroinitiators for the polymerization of oligo(propylene oxide) monomethacrylate by ATRP in a 1/3 v/v water/methanol mixture and in a 1/1 v/v water/1-propanol mixture. Deviations from first-order kinetics with respect to the monomer concentration were observed indicating that termination reactions were taking place. However, linear plots were obtained, when ln[M] 0 /[M] was plotted against time 2/3 as suggested by Fischer. The effect on the control of the polymerization by adding Cu(II)Br 2 to the polymerization medium has been investigated. When 10 mol-% of Cu(II)Br 2 was substituted for Cu(I)Br, normal first-order kinetics were observed. A large reduction in the rate of polymerization was observed for the polymerization initiated by bifunctional PEO10 000 initiator, but almost no reduction in the rate of polymerization was observed, when the bifunctional PEO16 000 initiator was used. When the polymerizations were conducted in 1/1 v/v water/1-propanol unexpectedly high rates of polymerization were observed.

Synthesis of 1‐chloro‐1‐phenylethyl‐telechelic polyisobutylene, a new potential macroinitiator by living cationic polymerization

1-Chloro-1-phenylethyl-telechelic polyisobutylene (PIB) was synthesized by living carbocationic polymerization (LCCP). LCCP of isobutylene was induced by a difunctional initiator in conjunction with TiCl4 as coinitiator in the presence of N,N-dimethylacetamide in CH2Cl2/hexane (40:60 v/v) solvent mixture at −78°C. After complete isobutylene conversion a small amount of styrene was added leading to a rapid crossover reaction and thus to the attachment of short outer polystyrene (PSt) blocks to the PIB segment. Quenching the living polymerization of styrene yielded 1-chloro-1-phenylethyl terminal groups. The resulting telechelic polymer (Cl-PSt-PIB-PSt-Cl) is a potential new macroinitiator for atom transfer radical polymerization of a variety of vinyl monomers.