Search results for "Polymer architecture"
showing 10 items of 15 documents
Amphiphilic HPMA-LMA copolymers increase the transport of Rhodamine 123 across a BBB model without harming its barrier integrity.
2012
Abstract The successful non-invasive treatment of diseases associated with the central nervous system (CNS) is generally limited by poor brain permeability of various developed drugs. The blood–brain barrier (BBB) prevents the passage of therapeutics to their site of action. Polymeric drug delivery systems are promising solutions to effectively transport drugs into the brain. We recently showed that amphiphilic random copolymers based on the hydrophilic p(N-(2-hydroxypropyl)-methacrylamide), pHPMA, possessing randomly distributed hydrophobic p(laurylmethacrylate), pLMA, are able to mediate delivery of domperidone into the brain of mice in vivo. To gain further insight into structure–propert…
Can Soft Models Describe Polymer Knots?
2020
Similar to macroscopic ropes and cables, long polymers create knots. We address the fundamental question whether and under which conditions it is possible to describe these intriguing objects with crude models that capture only mesoscale polymer properties. We focus on melts of long polymers which we describe by a model typical for mesoscopic simulations. A worm-like chain model defines the polymer architecture. To describe nonbonded interactions, we deliberately choose a generic "soft" repulsive potential that leads to strongly overlapping monomers and coarse local liquid structure. The soft model is parametrized to accurately reproduce mesoscopic structure and conformations of reference p…
Grafting of hyperbranched polymers: From unusual complex polymer topologies to multivalent surface functionalization
2013
Abstract In this feature article, the grafting of hyperbranched polymers to different substrates is reviewed. Both grafting onto macromolecules with different topologies (homogeneous grafting) and the resulting complex polymer architectures containing highly branched segments as well as their applications are discussed. In the second part grafting of hyperbranched polymers on surfaces, i.e., planar surfaces and spherical particles (heterogeneous grafting), with respect to specific applications, such as bio-repellent surfaces or soluble carbon nanotubes is described. In all cases, the one-step synthesis and the resulting highly branched topology of the hyperbranched building blocks is benefi…
Linear versus Three-Arm Star Polybutadiene: Effects of Polymer Architecture on the Thermodynamic Solution Behavior
2012
The interaction of linear and of three-arm star polybutadiene (PB) with THF was studied in the temperature range between 25 and 55 °C. Information for dilute solution rests on light scattering experiments; Flory–Huggins interaction parameter χ stem from vapor pressure measurements as a function of φ, the volume fraction of polymer. Despite the minute divergence in the architecture, the second osmotic virial coefficients of the two PBs differ noticeably. The present work demonstrates that these disparities become much more pronounced as φ increases and that they depend strongly on temperature. These findings are interpreted on the basis of an approach accounting for the effects of chain conn…
Langmuir-Blodgett films of biocompatible poly(HPMA)-block-poly(lauryl methacrylate) and poly(HPMA)-random-poly(lauryl methacrylate): influence of pol…
2010
Membranes based on functional biocompatible polymers can be regarded as a useful model system to study biological interactions, e.g. antibody-antigen interactions or protein polymer interactions. These model systems may give a better insight into these processes and may help to find suitable polymeric structures offering biocompatibility as well as reduced polymer protein interaction. In this respect, Langmuir-Blodgett (LB) layer formation at the air/water (A/W) interface is studied in respect to polymer architecture in this article. For this purpose, narrowly distributed N-(2-hydroxypropyl)-methacrylamide (HPMA) random and block copolymers have been prepared by the RAFT polymerization meth…
Viscometric study of mixtures of neutral and charged polymers in aqueous solution
1997
The viscosity behaviour of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B) such as polystyrene sulfonate (PSS)-polyvinylpyrrolidone (PVP) and polylysine (PLL)-PVP has been studied at 25°C. The intrinsic viscosity and viscosity interaction parameter of each polymer in water have been determined and have served us to estimate the compatibility of the different mixtures according to two different methodologies: (i) mixtures of two polymers in water as solvent and (ii) mixtures of either polymer A OFB in a solvent formed by either polymer B or A in water ("polymer solvent method"). By comparing the experimental and theoretical viscosity data it is clearly seen that: m…
The effect of free polymer on the interactions and the glass transition dynamics of microgel colloids.
2002
By studying the phase behaviour and the short range order of polystyrene microgel colloids in a good solvent we demonstrated that these particles can be considered as hard spheres or nearly hard spheres if the internal cross link density is made sufficiently high. A binary mixture of 1:50 crosslinked (1 crosslink per 50 monomers) particles with a size ratio R(small)/R(large) = 0.83 and a number ratio N(small)/N(large) = 2.7 was characterized with respect to the short range order and glass transition dynamics. We found that this mixture can be mapped onto a one-component hard sphere system with an effective polydispersity of 11%, even though for the particle interactions an inverse power pot…
Impact of Amino-Functionalization on the Response of Poly(ethylene glycol) (PEG) to External Stimuli
2022
It is shown that amino-functionalization of poly(ethylene glycol) (PEG) with the comonomer N,N-diethyl glycidyl amine (DEGA) triggers the emergence of extraordinary stimuli responsiveness and phase behavior of PEG. In dependence of the solution pH, tapered PEG-co-PDEGA exhibits a highly cooperative two-step inverse phase transition with respect to temperature. The polymer forms dispersed metastable nanoglobules in the medically relevant temperature range around human body temperature. Independently, cloud points can be adjusted between 40 and 90 °C via the pH of the solution. Changing the polymer architecture to a block structure, in pronounced contrast, the polymer exhibits a gradual growt…
Correlation between polymer architecture, mesoscale structure and photovoltaic performance in side-chain-modified poly(p-arylene-ethynylene)-alt-poly…
2011
Abstract Recent investigations have shown that an anthracene containing poly( p -arylene-ethynylene)-alt-poly( p -arylene-vinylene) statistical copolymer consisting of a well defined conjugated backbone, along which linear and branched alkoxy side chains are attached in a random manner, yields, compared to its counterparts with regular side chain substitution, an improved performance in polymer [6,6]:-phenyl-C 61 -butyric acid methyl ester (PCBM) bulk-heterojunction solar cells. The microscopic origin for the improved power conversion efficiency ( η ≈ 3.8%) of the statistical copolymer – which is the best in its material class – has not been resolved. We conducted grazing incidence wide-an…
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 …