Polymerization Of Tert-butyl Acrylate Research Articles

PH-responsive AIE-active Polyethylene-based Block Copolymers

A novel synthetic strategy towards pH-responsive aggregation-induced emission (AIE)-active tetraphenylethene (TPE)-functionalized polyethylene-based block copolymers is presented. Tris(3-(4-(1,2,2-triphenylvinyl)phenoxy)propyl)borane was used to initiate the polyhomologation of dimethylsulfoxonium methylide to afford well-defined α-TPE-ω-OH linear polyethylenes (PE). The terminal hydroxyl groups were transformed to atom transfer radical polymerization (ATRP) initiating sites by esterification with α-bromoisobutyryl bromide, followed by polymerization of tert-butyl acrylate (tBA) to provide TPE-PE-b-PtBA block copolymers. After hydrolysis of the tBu group to COOH group, the corresponding pH-responsive TPE-PE-b-PAA block copolymers were obtained. All synthesized block copolymers revealed AIE behavior either in solution or bulk. Due to the pH-responsivity of PAA chains, the aggregation state at different pH and consequently the fluorescence intensity changed. Also, the synthesized block copolymers exhibited ion-specificity fluorescence properties.

Synthesis of H-shaped complex macromolecular structures by combination of atom transfer radical polymerization, photoinduced radical coupling, ring-opening polymerization, and iniferter processes

Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD-type H-shaped complex copolymer. First, a-benzophenone functional polystyrene (BP-PS) and poly( methyl methacrylate) (BP-PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of e-caprolactone (CL) by using PS-b-PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL-PSPMMA- PCL. Finally, the polymerization of tert-butyl acrylate (tBA) via iniferter process gave the targeted H-shaped block copolymer

Rapid Synthesis of Functional Polymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization of an Acidic Monomer

The combination of a highly reactive monomer, 2-(methacryloyloxy)ethyl succinate (MES), and active catalyst systems, e.g., Cu(I) complexed with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), allows rapid formation of poly(carboxylic acid) brushes by atom transfer radical polymerization (ATRP) from a surface. ATRP from initiators immobilized on Au-coated Si wafers yields films with an ellipsometric thickness of 120 nm in less than 15 min. To the best of our knowledge, this is the first example of direct ATRP of protonated acidic monomers that is capable of yielding such thick films, and MES polymerizes much more rapidly than methacrylic acid both in solution and on a surface. The MES films are attractive for a number of applications, including immobilization of proteins. Assuming that a lysozyme monolayer has a thickness of 2 nm, a 55 nm poly(MES) brush binds ∼70 monolayers of lysozyme via ion-exchange interactions. Additionally, when derivatized with nitrilotriacetate−Cu2+ complexes, poly(MES) films bind ∼34 monolayers of BSA through metal-ion affinity interactions (assuming a BSA monolayer thickness of 4 nm). These binding capacities are similar to those of poly(acrylic acid) brushes prepared by polymerization of tert-butyl acrylate and subsequent hydrolysis, but the poly(MES) synthesis is a one-step, aqueous process.

Behavior of Surface-Anchored Poly(acrylic acid) Brushes with Grafting Density Gradients on Solid Substrates: 1. Experiment

We describe experiments pertaining to the formation of surface-anchored poly(acrylic acid) (PAA) brushes with a gradual variation of the PAA grafting densities on flat surfaces and provide detailed analysis of their properties. The PAA brush gradients are generated by first covering the substrate with a molecular gradient of the polymerization initiator, followed by the “grafting from” polymerization of tert-butyl acrylate (tBA) from these substrate-bound initiator centers, and finally converting the PtBA into PAA. We use spectroscopic ellipsometry to measure the wet thickness of the grafted PAA chains in aqueous solutions at three different pH values (4, 5.8, and 10) and a series of ionic strengths (IS). Our measurements reveal that at low grafting densities, σ, the wet thickness of the PAA brush (H) remains relatively constant, the polymers are in the mushroom regime. Beyond a certain value of σ, the macromolecules enter the brush regime, where H increases with increasing σ. For a given σ, H exhibits a ...

Drug release behavior of poly(ε-caprolactone)-b-Poly(acrylic acid) Shell Crosslinked Micelles below the Critical Micelle Concentration

To explore the potential of shell crosslinked micelle (SCM) as a drug carrier, the drug release behavior of poly(e-caprolactone)-b-poly(acrylic acid) (PCL-b-PAA) SCMs was investigated. PCL-b-PAA was synthesized by ring opening polymerization of e-caprolactone and atom transfer radical polymerization oftert-butyl acrylate, followed by selective hydrolysis oftert-butyl ester groups to acrylic acid groups. The resulting amphiphilic polymer was used to prepare SCMs by crosslinking of PAA corona via amidation chemistry. The drug release behavior of the SCMs was studied, using pyrene as a model drug, and was compared with that of non-crosslinked micelles, especially below the critical micelle concentration (CMC). When the shell layers were crosslinked, the drug release behavior of the SCMs was successfully modulated at a controlled rate compared with that of the non-crosslinked micelles, which showed a burst release of drug within a short time.

Polymerization of t-butyl acrylate using organoaluminum complexes and correlation between main-chain tacticity and glass transition temperature of the obtained polymers

The polymerization of tert-butyl acrylate (tBA) was performed with triethylaluminum-(−)-sparteine, triethylaluminum–tertiary phosphine, triethylaluminum–n-BuLi and bis(2,6-di-tert-butyl-4-methylphenoxide)methylaluminum–t-BuLi complexes in toluene. The poly(tBA)s obtained with these initiators were rich in syndiotactic diad as observed by 1H NMR analysis. On the basis of the triad and tetrad stereochemical information of the poly(tBA)s obtained using triethylaluminum-(−)-sparteine and triethylaluminum–n-BuLi, the polymerization reactions were found to obey Bernoullian statistics. Glass transition temperatures of the poly(tBA)s were measured by differential scanning calorimetry (DSC). A syndiotactic poly(tBA) (racemo (r) diad content: 65%) and an isotactic one (r=19%) exhibited higher glass transition temperature (50 and 43°C, respectively) than an atactic one (r=50%,Tg=21°C).

Synthesis of block copolymers by atom transfer radical polymerization oftert-butyl acrylate with poly(oxyethylene) macroinitiators

Poly(oxyethylene)s terminated at both ends with 2-bromopropionate end-groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert-butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert-butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.

Specific Salt Effect of Lithium Perchlorate in Living Anionic Polymerization of Methyl Methacrylate and tert-Butyl Acrylate

Living anionic polymerization of methyl methacrylate can be achieved at −40 °C in tetrahydrofuran (THF) and at −78 °C in toluene/THF (9/1 v/v) using (1,1-diphenylhexyl)lithium as the initiator in the presence of lithium perchlorate (LiClO4) as the additive. Polymerization of tert-butyl acrylate also proceeds in a living manner at −78 oC in THF. Polymers with narrow molecular weight distributions and high initiator efficiencies can be obtained. The use of lithium perchlorate retards the rate of polymerization. The ratio of LiClO4 to initiator has a greater influence in determining the control of polymerization. The beneficial effect of lithium perchlorate is attributed to its efficient interaction with growing ester−enolate ion pairs.