Search results for "polymerization"
showing 10 items of 1689 documents
Controlled Synthesis of Linear Polymers with Highly Branched Side Chains by “Hypergrafting”: Poly(4-hydroxy styrene)-graft-hyperbranched Polyglycerol
2012
Linear polymers with hyperbranched side chains are unusual macromolecular structures due to their high number of functional groups in the side chains as well as their potential cylindrical conformation in bulk or solution. In a three-step synthesis combining anionic and oxy-anionic polymerization, hyperbranched polyglycerol was “hypergrafted” from linear poly(4-hydroxy styrene) macroinitiators to yield poly(4-hydroxy styrene)-graft-hyperbranched polyglycerol. Successful grafting with control over molecular weight (10–31 kg·mol–1) and low PDIs (<1.4) was shown by various characterization techniques. All polymers have a high side chain density, due to rapid transfer of the initiating function…
Specialty and advanced polymers by carbocationic macromolecular engineering
1993
This study briefly surveys a variety of new advanced polymeric materials and controlled synthetic processes available by carbocationic macromolecular engineering techniques and having potential commercial interest. These recent developments, mainly by living carbocationic polymerization, have led to new opportunities in polymerization process control, and in designing microstructure, functionality, molecular weight and molecular weight distribution (MWD) and thus properties of a wide variety of unique polymer systems. The fundamentals of these new emerging technologies and the novel materials offered by them, such as macromonomers, telechelics, polymers with pendant functional groups (liqui…
Polysiloxane-backbone block copolymers in a one-pot synthesis: a silicone platform for facile functionalization.
2012
Block copolymers consisting exclusively of a silicon-oxygen backbone are synthesized by sequential anionic ring-opening polymerization of different cyclic siloxane monomers. After formation of a poly(dimethylsiloxane) (PDMS) block by butyllithium-initiated polymerization of D3, a functional second block is generated by subsequent addition of tetramethyl tetravinyl cyclotetrasiloxane (D4(V) ), resulting in diblock copolymers comprised a simple PDMS block and a functional poly(methylvinylsiloxane) (PMVS) block. Polymers of varying block length ratios were obtained and characterized. The vinyl groups of the second block can be easily modified with a variety of side chains using hydrosilylation…
Some linear and branched macromolecules by ring-opening polymerization
1993
In the first part the ring-opening polymerization of some macrocyclic ether-acetals is briefly described. Of special interest are acetal polymers with functional groups, for instance C=C-double bonds. Appropriate unsaturated monomers and their polymerizability are discussed. The second part deals with the polymerization of oxazolines, substituted in 2- and/or 4-position. Branched polymers are obtained by copolymerization of 2-ethyl-2-oxazoline with 2-hexyl-2-oxazoline or 2-undecyl-2-oxazoline. The properties of the random copolymers and corresponding block copolymers are compared. By a “mixed mechanism technique” a block copolymer composed of a poly(tert -butyl methacrylate) block and a pol…
Solution Properties of Polysarcosine: From Absolute and Relative Molar Mass Determinations to Complement Activation
2018
Polysarcosine (pSar) was one of the first polymers synthesized in a controlled living manner, but it was only recently when it was reconsidered as a promising alternative for poly(ethylene glycol) (PEG) in biomedical applications. Despite receiving more and more attention, very little is known about the solution properties of pSar, such as coil dimensions and thermodynamic interactions. In this article, we report on these properties of pSar with degrees of polymerization 50 < X-n < 400 that were prepared by controlled living ring-opening polymerization. The polymers are characterized by gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, dynamic and static light scattering (SL…
Tunable dynamic hydrophobic attachment of guest molecules in amphiphilic core–shell polymers
2016
In this study, synthesis and dynamic properties of amphiphilic core–shell polymers are reported as monitored through their interaction with small amphiphilic molecules. Brush-like structures are formed with a hydrophobic core surrounded by a hydrophilic shell utilizing controlled radical addition–fragmentation chain transfer (RAFT) polymerization of macromonomers consisting of linear polyglycerol chains attached to alkylene methacrylate. Continuous wave electron paramagnetic resonance (CW EPR) spectroscopy is employed to study how the amphiphilic, paramagnetic spin probe 16-DSA (16-doxyl stearic acid) interacts with polymers of different alkylene chain lengths in their hydrophobic cores and…
Living Polymer Chains with Predictable Molecular Weight and Dispersity via Carbanionic Polymerization in Continuous Flow: Mixing Rate as a Key Parame…
2016
Aiming at systematic variation of the parameter dispersity, Đ (or “polydispersity”), living polymers with predictable dispersity (Đ = 1.15–2.20) and controlled molecular weights (Mn = 3200–18 500 g mol–1) were prepared via carbanionic polymerization. The approach relies on a continuous flow reactor equipped with a tangential four-way jet micromixing device. By varying the total flow rate, the mixing efficiency of the initiator (sec-BuLi) and the corresponding vinyl monomers is controlled, resulting in polymers with predefined dispersity, while the number-average molecular weight, Mn, is kept constant. In this manner living polystyrene (PS), poly(p-methylstyrene) (PpMeS), and poly(2-vinylpyr…
Block Copolymers Build-up of Electron and Hole Transport Materials
2004
In this article we describe the synthesis of various monomers modified with triphenyl-1,3,5-triazine side groups as electron transport moieties. By nitroxide-mediated polymerization with a TEMPO unimer it was possible to obtain polymers with a narrow polydispersity. Furthermore, by living radical polymerization block copolymers were obtained from these monomers. Therefore, microphase separated structures are accessible which possess hole conducting moieties in one phase and electron conducting moieties in the other phase.
Functional Diblock Copolymers for the Integration of Triboluminescent Materials into Polymer Matrices
2008
This work describes the synthesis and use of new diblock copolymers to integrate functional inorganic particles into a polymer matrix. These diblock copolymers were synthesized by nitroxide-mediated polymerization (NMP) from styrene and two styrene-like monomers with protected functional groups for the later connection to the functional inorganic material. It was possible to keep the polydispersity of the block copolymers around or below 1.2 and to preset the length of the functional block to about 20 monomers or 10 mol-% of monomers. The groups for the surface functionalization (amino groups or chelating ligands) were obtained in their free form by polymer analogous reactions. As an exampl…
Mechanistic study on the metallocene-based tandem catalytic coordinative chain transfer polymerization for the synthesis of highly branched polyolefi…
2021
Abstract Creation and control of long-chain branches (LCBs) in coordination polymerization of olefins is an enduring focus of research in both academia and industry. We have recently introduced a tandem catalytic coordinative chain transfer polymerization reaction where upon the concerted function of the polymerization catalyst, the chain transfer agent (CTA), and the displacement catalyst, a highly branched microstructure can be formed. Here we introduce a new tandem catalytic system using Et(Ind)2ZrCl2 as the polymerization catalyst. Despite the optimal reaction temperature for the cooperative function of catalyst components is lower than the ideal temperature for the productivity of the …