Search results for "Note"
showing 10 items of 10709 documents
The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanica…
2021
Abstract The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation…
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…
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 …
Linear–dendritic block copolymers: The state of the art and exciting perspectives
2011
Concurrent with the rapid development of both dendrimers and hyperbranched polymers, a novel class of block copolymer architectures has emerged from the combination of these dendritic architectures with linear chains, the “linear–dendritic block copolymers” (LDBCs). This review gives a comprehensive summary of the state of the art in this rapidly developing field from pioneering early work to promising recent approaches.The different strategies leading to these hybrid architectures with either perfect dendrimer/dendron building blocks or imperfect, yet more conveniently accessible hyperbranched segments, are reviewed and compared. The consequences of the unusual polymer topology for supramo…
Topology-Sensitive Microfluidic Filter for Polymers of Varying Stiffness
2017
The separation of polymers based on their size, rigidity, and topology is an essential but also highly challenging task for nanoscience and engineering. Using hybrid molecular dynamics simulations that correctly take into account hydrodynamics, we have designed microfluidic channels for separating linear from ring polymers in dilute solutions. We establish that the transport velocity of the polymers is independent of their topology and rigidity when the channel walls are smooth and repulsive. However, when the walls are decorated with attractive spots arranged on lines parallel to the flow, ring polymers exhibit an order of magnitude higher transport velocity compared to linear chains. The …
Cylindrical polymer brushes – Anisotropic building blocks, unimolecular templates and particulate nanocarriers
2016
Abstract This article presents an overview of the latest key developments and research activities in the area of cylindrical polymer brushes (CPBs), also known as ‘molecular bottlebrushes’. CPBs consist of a polymer backbone containing polymer side chains that cause the backbone to extend and adopt a worm-like conformation. The extent of backbone stretching and the aspect ratio of CPBs is determined by the length and grafting density of the side chains. The latest developments in controlled/living polymerisation techniques led to novel and more efficient ways of producing delicate polymer architectures, such as block copolymer CPBs, and resulted in a considerable expansion of the field of a…
Controlling supramolecular polymerization through multicomponent self-assembly
2016
The self-assembly into supramolecular polymers is a process driven by reversible non-covalent interactions between monomers, and gives access to materials applications incorporating mechanical, biological, optical or electronic functionalities. Compared to the achievements in precision polymer synthesis via living and controlled covalent polymerization processes, supramolecular chemists have only just learned how to developed strategies that allow similar control over polymer length, (co)monomer sequence and morphology (random, alternating or blocked ordering). This highlight article discusses the unique opportunities that arise when coassembling multicomponent supramolecular polymers, and …
Hyperbranched polymer architectures: From Flory's AB(f-1) polycondensates to controlled structures
2020
Abstract Celebrating the 100th anniversary of Staudinger's “macromolecular concept”, polymer scientists critically evaluate the past developments and future challenges of polymer science, asking: Quo vadis, Macromolecular Science? The main focus in Polymer Science has been on linear polymers or crosslinked systems (elastomers and thermosets) until the late 1980ies. The advent of dendritic polymers, i.e. dendrimers and hyperbranched polymers (HBPs) attracted wide-spread attention in the polymer community. This article gives a brief overview of the developments in the area of hyperbranched polymers and demonstrates that they have since become a novel class of polymer materials.